From Old Irish áithesach, áthasach (“victorious, successful”), from áithes, áthas (“sharpness, keenness; successful feat, exploit, victory; joy”). By surface analysis, áitheas (“success, victory”) + -ach (adjectival ending).
áitheasach (genitive singular masculine áitheasaigh, genitive singular feminine áitheasaí, plural áitheasacha, comparative áitheasaí)
| singular | plural (m/f) | |||
|---|---|---|---|---|
| Positive | masculine | feminine | (strong noun) | (weak noun) |
| nominative | áitheasach | áitheasach | áitheasacha | |
| vocative | áitheasaigh | áitheasacha | ||
| genitive | áitheasaí | áitheasacha | áitheasach | |
| dative | áitheasach | áitheasach; áitheasaigh (archaic) |
áitheasacha | |
| Comparative | níos áitheasaí | |||
| Superlative | is áitheasaí | |||
| radical | eclipsis | with h-prothesis | with t-prothesis |
|---|---|---|---|
| áitheasach | n-áitheasach | háitheasach | not applicable |
Note: Certain mutated forms of some words can never occur in standard Modern Irish.
All possible mutated forms are displayed for convenience.