Modal and Auxiliary Verbs

Unlike English, Irish has almost no dedicated modal verbs (like “can”, “must”, “should”). Instead, it expresses these concepts using a variety of idiomatic phrases. These phrases often involve the verb bí (to be), the copula is, and various prepositions that assign the logical subject of the action.

This page provides a comprehensive reference for these common modal constructions.

General Principles

How Modality is Expressed

Most modal meanings are conveyed through set phrases rather than single verbs.

• Phrases with bí or the copula is: The most common patterns use the verb bí (e.g., tá orm - I must) or the copula is (e.g., is féidir liom - I can).
• Conditional Forms for Politeness: To soften a statement or make it more polite (e.g., “would have to”, “could”, “should”), the conditional form of the auxiliary verb is used. tá becomes bheadh, and is becomes ba.
• Verbs with Secondary Modal Meanings: A few regular verbs take on a modal meaning in certain contexts, especially in the future or conditional tense. For example, caithfidh (literally “will spend/throw”) means “must”, and glacfadh (literally “would accept”) can mean “should”.

Objective vs Subjective Modality

In many copula-based phrases, the choice of preposition changes the meaning from an objective fact to a subjective assessment.

• do for Objective Statements: Using the preposition do (to/for) indicates an objective necessity or a factual obligation. The logical subject is seen as being under a general or moral duty.
  • B’éigean dom imeacht - I had to leave (it was a necessity for me).
  • Is fearr dom fanacht - I had better stay (it is better for me to stay).
• le for Subjective Assessments: Using the preposition le (with) indicates a personal opinion, feeling, or preference.
  • Is maith liom tae - I like tea (it is good with me).
  • B’fhearr liom fanacht - I would prefer to stay (it would be better with me to stay).

Complements: Verbal Nouns vs go/nach Clauses

Modal phrases are usually completed by either a verbal noun phrase or a clause introduced by go (that) or nach (that… not).

• Verbal Noun Phrases: This is the most common and preferred way to complete a modal phrase.
  • Ba mhaith liom teacht - I would like to come.
• go/nach Clauses: These are used when the subject of the modal phrase is different from the subject of the following action, or to express a different kind of modality (see below).
  • Ba mhaith liom go dtiocfá - I would like you to come.

Deontic vs Epistemic Modality

The choice between a verbal noun and a go/nach clause can change the type of modality being expressed, especially for concepts like “must” and “can”.

• Deontic Modality (Action): This refers to permission, obligation, or ability to perform an action. It is usually expressed with a verbal noun phrase.
  • Caithfidh sé an bád a phéinteáil - He must paint the boat (he is obliged to do it).
• Epistemic Modality (Belief): This refers to a speaker’s assessment of how likely something is to be true (“it must be that…”, “it can’t be that…”). It is usually expressed with a go/nach clause.
  • Caithfidh go bpéinteálann sé an bád - It must be that he paints the boat (I assume this is true).

Negation

Irish clearly distinguishes between negating the modal concept itself (external negation) and negating the action being discussed (internal negation).

• External Negation (ní): Using the negative particle ní negates the modal phrase.
  • Ní chaithfidh sé imeacht - He does not have to leave. (The “having to” is negated).
• Internal Negation (gan): Using gan (without) before the verbal noun negates the action.
  • Caithfidh sé gan imeacht - He must not leave. (The “leaving” is negated).

This clarity allows for double negatives, which usually create a strong affirmative statement.

• Ní féidir liom gan é a dhéanamh - I cannot not do it / I can’t help but do it.

Must (Obligation and Necessity)

Using caithfidh

The future tense of the verb caith (to spend, throw, wear) is the most common way to say “must”.

• Formula: caithfidh + Subject + Verbal Noun / go-clause
• Caithfidh mé imeacht - I must go.
• Caithfidh tú é a dhéanamh - You must do it.

Tense and Usage:

• In the past, the conditional form is often used: Chaithfinn imeacht - I had to go / I would have to go.
• After má (if), the habitual present caitheann is used: Má chaitheann sé imeacht - If he must go.

Negation:

• External (ní): Ní chaithfidh sé imeacht - He does not have to leave.
• Internal (gan): Caithfidh sé gan imeacht - He must not leave. (Less common than níl cead aige...).

Using bí + ar

This construction implies a duty or burden placed “on” someone.

• Formula: Form of bí + ar + Logical Subject + Verbal Noun
• Tá orm imeacht - I must go. (Literally: “Is on-me to go”)
• Bheadh ar Sheán teacht - Seán would have to come.

Using tar + ar

This is similar to bí + ar but often implies a necessity that arose or “came upon” someone.

• Formula: Form of tar + ar + Logical Subject + Verbal Noun
• Tháinig orm imeacht - I had to go. (Literally: “Came on-me to go”)
• Ní thiocfaidh ort pingin a íoc - You will not have to pay a penny.

Using is éigean do

This phrase expresses compulsion or necessity, especially in the past tense.

• Formula: Form of Copula + éigean + do + Logical Subject + Verbal Noun
• B’éigean dom é a dhéanamh - I had to do it. (Literally: “Was compulsion to-me it to do”)

Using ní mór do

This is a formally negative phrase that means “must”.

• Formula: ní mór + do + Logical Subject + Verbal Noun
• Ní mór duit a bheith anseo - You must be here. (Literally: “Is-not big to-you to be here”)
• Ní mór dom dul ar scoil - I must go to school.

Using ní foláir do/le

This phrase also uses a formal negative to mean “must”. The choice of preposition distinguishes between objective necessity (do) and subjective assessment (le).

• Objective (do): Ní foláir dom é a rá - I must say it (circumstances require it).
• Subjective (le): Ní foláir liom é a rá - I think I should say it.

Using bí + le + ag

This construction, similar to a gerundive in Latin, expresses that something “is to be done”. It is used with transitive verbs.

• Formula: Form of bí + Object + le + Verbal Noun + ag + Logical Subject
• Tá litir le scríobh agam - I have a letter to write / I must write a letter.

Using bí + ag + le

• Formula: Form of bí + ag + Logical Subject + le + Verbal Noun
• Tá agam le dul - I have to go.

Using bí + d’fhiacha ar

This is a less common way to express obligation, literally meaning “to be in debt to do something”.

• Formula: Tá sé d'fhiacha ar + Logical Subject + Verbal Noun
• Tá sé d’fhiacha orm teacht - I am obliged to come.
• Other nouns like iallach (compulsion), oibleagáid (obligation), or dualgas (duty) can be used instead of fiacha.

Epistemic “Must”

To express an assumption or logical conclusion (“it must be that…”), a go-clause is used.

• Past: b’éigean dó go...
  • B’éigean dó gur thit a gcodladh orthu - They must have fallen asleep.
• Present: ní foláir nó (go)...
  • Ní foláir nó tá sí tinn - She must be ill.
• Present/Future: caithfidh (sé) go...
  • Caithfidh go bhfuil sí ann - She must be there.
• Present: ní féidir nó (go)...
  • Ní féidir nó tá tú faoi dhraíocht - You must be under a spell.

Should (Advice and Recommendation)

Using is ceart do

This phrase means “it is right/correct for someone to…”

• Formula: Form of Copula + ceart + do + Logical Subject + Verbal Noun / go-clause
• Is ceart do Sheán teacht - Seán should come.
• Ba cheart duit é a dhéanamh - You should do it.

Using is cóir do

This is very similar to is ceart do and means “it is proper/just for someone to…”

• Formula: Form of Copula + cóir + do + Logical Subject + Verbal Noun / go-clause
• Ba chóir duit é a dhéanamh - You should do it.

Using glacfadh

• Formula: Conditional of glac + Subject + Verbal Noun
• Ghlacfainn imeacht - I should better go.

Using d’fhéad

• Formula: Preterite of féad (+ do) + Subject + Verbal Noun
• D’fhéad tú labhairt leis - You should have spoken to him.

Expressing “At least should”

Phrases like is gann do, is beag an rud do, or is ar a laghad do express that something is the minimum that should be done.

• Is gann dó é - It’s the least he should do.
• Is beag an rud dom labhairt leis - At least I should speak to him.

Other Ways to Express “Should”

• Imperative (3rd Person): The 3rd person imperative is often translated as “should”.
  • Tagadh Seán! - Seán should come! / Let Seán come!
• Future Tense: For questions like “Shall I…?” or “Shall we…?”, the future tense is used.
  • An gcabhróidh mé leat? - Shall I help you?
• Conditional Tense: The conditional can often be translated as “should”.
  • Dhéanfadh sé cúis, dar liom - It should suffice, I think.

Epistemic “Should”

To express an opinion about what is likely (“he should have arrived by now”), the same structures are used, often with a perfective verbal noun phrase or a conditional go-clause.

• Ba cheart dó a bheith tagtha faoi seo - He should have arrived by now.
• Ba cheart go mbeadh an teach críochnaithe - The house should be finished.

Had Better / Prefer to

Using is fearr do

This construction means “it is better for someone to…”, equivalent to “had better”.

• Formula: Form of Copula + fearr + do + Logical Subject + Verbal Noun
• Is fearr dom teacht - I had better come.
• B’fhearr do Sheán teacht - Seán had better come / should have come.

Using is córa do / is cirte do

These comparatives of cóir (right/proper) and ceart (right/correct) can also be used to mean “had better”.

• Sin mar is córa duit dul chun cainte leis - That’s why you should all the more go and talk to him.
• Ba chirte dom a rá… - I should rather say…

Can (Ability and Possibility)

Using is féidir le/do

This is the most common way to express “can”. le indicates subjective ability, while do suggests objective possibility.

• Formula: Is féidir + le/do + Logical Subject + Verbal Noun
• Is féidir liom Gaeilge a scríobh - I can write Irish.
• Ní féidir do na páistí é a dhéanamh - It is not possible for the children to do it.

Using tig le

The verb tar (to come), in its variant form tig, is used with le to mean “can”.

• Formula: Form of tig + le + Logical Subject + Verbal Noun
• Tig le Pól é a dhéanamh - Paul can do it.
• Thiocfadh le Pól é a dhéanamh - Paul could do it.

Using is acmhainn do

This phrase specifically means “can afford to” or “has the resources to”.

• Formula: Is acmhainn + do + Logical Subject + Verbal Noun
• Is acmhainn dó teach a cheannach - He can afford to buy a house.

Using bí in ann / ábalta

These phrases mean “to be able” or “to be capable of”.

• Formula: Form of bí + Subject + in ann/ábalta + Verbal Noun
• Tá mé in ann Gaeilge a scríobh - I am able to write Irish. (Common in Connacht)
• Tá mé ábalta Gaeilge a scríobh - I am able to write Irish. (Common in Ulster and Munster)

Using féad

Féad is one of the few true modal verbs in Irish. It can be conjugated in all tenses.

• Formula: Form of féad + Subject + Verbal Noun
• Nach bhféadfá fanacht? - Couldn’t you stay?
• Féadfaidh sé teacht lá ar bith - He can come any day.

Using bí … ag for Learned Skills

For learned skills like languages or swimming, the “to have” construction is used.

• Formula: Tá + Skill (noun) + ag + Subject
• Tá Gaeilge agam - I can speak Irish. (Literally: “I have Irish”)
• Tá snámh agam - I can swim.

Negation and Double Negation

To say “cannot”, simply negate the modal construction: Ní féidir liom. A double negative (ní ... gan) means “cannot help but”.

• Ní féidir liom gan gáire a dhéanamh - I can’t help but laugh.

Epistemic “Can”

To express possibility (“it could be that…”), a go-clause is used, and the logical subject is usually omitted or is dó (to it).

• b'fhéidir go... - Perhaps… / It could be that…
  • B’fhéidir go bhfuil sé ann - Perhaps he is there.
• thiocfadh dó go... - It could be that…
  • Thiocfadh dó go ndearnadh botún - It could be that a mistake was made.
• ní féidir go... - It cannot be that…
  • Ní féidir go bhfuil rudaí chomh dona sin - It can’t be that things are so bad.

May (Permission)

Using bí cead ag

This is the standard way to ask for and grant permission. Cead means “permission”.

• Formula: Form of bí + cead + ag + Logical Subject + Verbal Noun
• An bhfuil cead agam dul go dtí an leithreas? - May I go to the toilet?
• Tá cead ag an bhfear fuisce a ól - The man may drink whiskey.

Using is ceadmhach do

Ceadmhach is the adjective “permitted” or “allowed”.

• Formula: Form of Copula + ceadmhach + do + Logical Subject + Verbal Noun
• Más ceadmhach dom sin a rá - If I may say so.
• Ní ceadmhach duit bean do dhearthár a bheith agat - You may not have your brother’s wife.

Using féadfaidh

The future tense of féad can also be used to grant permission.

• Formula: Féadfaidh + Subject + Verbal Noun
• Féadfaidh tú imeacht anois - You may go now.

Using is miste le/do

This phrase is used for polite requests, meaning “would you mind if…”.

• Formula: Ar mhiste leat/duit + …?
• Ar mhiste leat mé a dhul ansin? - Would you mind if I went there? / May I go there?
• The standard affirmative answer is formally negative: Ní miste - I don’t mind / Yes, you may.

Expressing “Not Allowed”

This is usually expressed by negating cead.

• Níl cead agat imeacht - You are not allowed to go.

To Like

Using is maith le

This is the most common way to say “to like”.

• Formula: Form of Copula + maith + le + Logical Subject + Object/Verbal Noun
• Is maith liom beoir - I like beer.
• The conditional form ba mhaith liom means “I would like”.
• Ba mhaith liom fuisce a ól - I would like to drink whiskey.
• To intensify, use breá (fine/lovely) instead of maith: Ba bhreá liom… - I would love to…

Using taitin … le

The verb taitin means “to please” or “to shine”.

• Formula: Form of taitin + Object + le + Logical Subject
• Taitníonn iasc liom - I like fish. (Literally: “Fish pleases with-me”)
• Thaitin an capall leis - He liked the horse.

Using bí dúil ag … i

This phrase expresses a strong liking or fondness for something.

• Formula: Form of bí + dúil + ag + Subject + i + Object
• Tá dúil agam sa tsiúl - I like hiking.

To Prefer / Would Rather

Using is fearr le

The comparative of maith (good) is fearr (better). Used with le, it means “to prefer”.

• Formula: Form of Copula + fearr + le + Logical Subject + Object/Verbal Noun
• Is fearr liom tae ná caife - I prefer tea to coffee.
• B’fhearr liom imeacht - I would rather leave.

Using is rogha le

The noun rogha (choice) can be used instead of fearr.

• Formula: Form of Copula + rogha + le + Logical Subject + Verbal Noun
• Is rogha liom imeacht anois - I would rather leave now.

To Want

Using bí … ó

This construction uses the preposition ó (from).

• Formula: Form of bí + Object + ó + Logical Subject
• Tá braon fuisce uaim - I want some whiskey. (Literally: “Is a drop of whiskey from-me”)
• Tá uaim fuisce a ól - I want to drink whiskey.

Using teastaigh … ó

The verb teastaigh can mean both “to want” and “to need”.

• Formula: Form of teastaigh + Object + ó + Logical Subject
• Teastaíonn arán uaidh - He wants/needs bread.

Using is mian le

This expresses a wish or desire.

• Formula: Form of Copula + mian + le + Logical Subject + Verbal Noun
• Is mian liom é a dhéanamh - I want/wish to do it.

Using ag iarraidh

The progressive form of iarr (to ask for, to try) is very commonly used to mean “to want”.

• Formula: Form of bí + Subject + ag iarraidh + Object/Verbal Noun
• An bhfuil tú ag iarraidh seacláide? - Do you want chocolate?
• Níl mé ag iarraidh éirí go fóill - I don’t want to get up yet.

Using bí fonn ar

This phrase means “to feel like” doing something.

• Formula: Form of bí + fonn + ar + Logical Subject + Verbal Noun
• Tá fonn orm é a dhéanamh - I feel like doing it.
• Bhí fonn codlata orm - I wanted to sleep / I felt sleepy.

To Need

Needing an Object

Several phrases express the need for a physical object.

• bí gá ag ... le ...: Tá gá aige leis an bpeann - He needs the pen.
• teastaigh ... ó ...: Teastaíonn arán uaidh - He needs bread.
• bí ... de dhíth ar ...: Tá braon fuisce de dhíth orm - I need some whiskey.

Needing to Do Something

To express that an action is necessary, is gá do is used. This is equivalent to “must”.

• Formula: Is gá + do + Logical Subject + Verbal Noun
• Is gá dom é a dhéanamh - I need to do it / I must do it.

”Not to Need” / “Don’t Have to”

The most common use of gá is in the negative, ní gá, which means “don’t have to” or “don’t need to”.

• Formula: Ní gá + do + Logical Subject + Verbal Noun
• Ní gá duit é a dhéanamh - You don’t need to do it.
• It is often used with ach (but/only) to mean “you only have to…”.
  • Ní gá duit ach clárú - You only have to register.

To Have

Irish does not have a single verb for “to have”. Instead, it uses the verb bí with different prepositions depending on the type of possession.

General Possession (tá … ag)

For general, transferable possessions (alienable possession).

• Formula: Tá + Object + ag + Subject
• Tá teach agam - I have a house.
• Níl carr againn - We don’t have a car.

States and Inalienable Possession (tá … ar)

For physical and emotional states, illnesses, and things that are part of you or an object (inalienable possession).

• Formula: Tá + State/Part + ar + Subject
• Tá ocras orm - I am hungry. (Literally: “Hunger is on me”)
• Tá slaghdán ar an gcailín - The girl has a cold.
• Tá féasóg ar an seanfhear - The old man has a beard.
• Cén t-ainm atá ort? - What is your name?

Ownership (is le)

To state ownership clearly, the copula is is used with the preposition le.

• Formula: Is + le + Owner + Object
• Is liom an carr seo - This car is mine.
• Is le Pól an teach - The house belongs to Paul.

bí as an Auxiliary Verb

The verb bí is the most common auxiliary verb in Irish. It is used for:

• Describing states and locations: Tá sé i nGaillimh - He is in Galway.
• With adjectives: Tá sé tinn - He is ill.
• Forming the progressive aspect: Tá sé ag ól - He is drinking.
• Forming perfect/passive states: Tá sé ólta aige - He has drunk it.
• Forming the intentional aspect: Tá sé ar tí ól - He is about to drink.
• Classification (without the copula): Tá sé ina mhúinteoir - He is a teacher.
• Forming “have” and modal constructions (as seen above).

déan as an Auxiliary Verb

The verb déan (to do/make) can be used as an auxiliary to add emphasis or for stylistic reasons.

Usage:

• To add insistence to a command: Déan é a cheannach! - Do buy it!
• To describe deliberate action or intent: Déanfaidh siad cuid acu a mharú - They will indeed kill some of them.
• To make a firm promise: Déanfaidh mé é a chloisint! - I will listen to it! (I promise!)
• In “only” sentences: Ach ní dhearna sé ach gáire - But he only laughed.
• To emphasise an action using a cleft sentence: An fear a fheiceáil a rinne tú - You saw the man. (Literally: “To see the man is what you did.”)
• As a substitute for other verbs in short answers: Ar ólais an tae? - Rinne. - Did you drink the tea? - Yes (I did).