Prefixes

In Irish, some adjectives and other modifying words can be attached to the beginning of a noun or another adjective as a prefix (réimír). This changes the meaning of the word and often triggers a sound change called a mutation. Understanding these prefixes is key to building vocabulary and understanding compound words.

While most descriptive adjectives come after the noun they modify, a few types always come before it:

• Pronominal adjectives like gach (every): gach teach (every house)
• Possessive pronouns like mo (my): mo theach (my house)
• Numbers like trí (three): trí theach (three houses)

Other descriptive adjectives can only be placed before a noun by turning them into a prefix.

How Prefixes Work

The way an adjective is used as a prefix depends on the word itself.

Prefix-only Adjectives

Some adjectives, like dea- (good) and droch- (bad), appear almost exclusively as prefixes.

• dea-bhád - a good boat
• drochbhád - a bad boat

Preferred Prefixes

For some adjectives, the prefix form is strongly preferred. A common example is sean- (old).

• seanfhear - an old man

Prefixes for Fixed Terms

Most adjectives are rarely used as prefixes. When they are, it is usually to form a specific, well-known compound noun or concept. In general use, they follow the noun.

• ardrí - High King
• sliabh ard - a high mountain

Intensifying Prefixes

Some prefixes act like adverbs, intensifying the meaning of the adjective or noun they are attached to. Common examples include an- (very), fíor- (truly), and ró- (too).

• an-mhaith - very good
• fíormhaith - really good
• rómhaith - too good

These can also modify nouns directly to create a new meaning.

• an-charr - a great car (literally “very-car”)

Mutation and Spelling Rules

Prefixes follow consistent rules for mutations and how they are written.

Mutations

Nearly all prefixes cause lenition on the following word.

• sean + bean → seanbhean (old woman)
• droch + bád → drochbhád (bad boat)

The main exception is the older prefix éa- (un-), which causes eclipsis.

Hyphenation

Prefixes and the words they modify are usually written as a single word.

• sean + fear → seanfhear (old man)

There are three main exceptions where a hyphen is required:

1. The prefixes an- (very) and dea- (good) are always followed by a hyphen.

   • an-bhean - a very good woman
   • dea-cheol - good music

2. A hyphen is used when two prefixes are joined together.

   • droch-sheanbhád - a bad old boat

3. A hyphen is used to separate two identical vowels or consonants.

   • ró-óg - too young
   • sean-nós - old style (a traditional style of singing)

Common Prefixes

This list includes some of the most frequently encountered prefixes.

Negative Prefixes

These prefixes add a negative meaning like “un-”, “dis-”, or “non-”.

Prefixes with Verbal Adjectives

The prefixes so-, do-, and in- are now almost exclusively used with verbal adjectives (participles) to indicate possibility.

Numbers as Prefixes

Numbers can also function as prefixes, often corresponding to English prefixes like “mono-”, “bi-”, and “tri-”.