As in many other languages, Irish adds prefixes to words to create new words. Becoming familiar with the prefixes below is an easy way to increase your vocabulary. Note that some prefixes are separated from the base word by a hyphen, and some prefixes cause lenition.
in-, un-, not-, over-
Examples: ceart (right) becomes aincheart (unjust), fios (knowledge) becomes ainfhiosracht (over-curious).
Example: maith (good) becomes an-mhaith (very good).
Example: déan (do, make) becomes athdéan (redo, remake).
chief, main, -headed
Example: litir (letter) becomes ceannlitir (capital letter).
Example: ceol (music) becomes comh-ceol (harmony).
Example: scéal (news, story) becomes dea-scéal (piece of good news).
red-, real, utter
Example: gráin (hatred) becomes dearg-ghráin (intense hatred).
bi-, di-, two-
Example: taobh (side) becomes déthaobhach (bilateral).
de-, dis-, in-, un-
Example: scéal (news, story) becomes díscéil (uninformative).
in-, un-, not-
Example: déanta (done, complete) becomes dodhéanta (impossible, hard to do).
Example: eochair (key) becomes ileochair (master key).
Example: creidte (believed) becomes inchreidte (believable).
Example: cead (permission) becomes lánchead (full permission).
Example: feiceáil (seeing) becomes reamhfheiceáil (foresight).
Example: insint (telling) becomes mioninsint (detailed report).
Example: riail (rule) becomes sár-riail (golden rule).
Example: minic (often) becomes ro-mhinic (too often).
Example: briste (broken) becomes so-bhriste (fragile, easily broken).