The f-future is the most common future formation in Old Irish. It is used in almost all A I and A II verbs, and as the future formation of the very common verb strong verb root ·icc. It is characterized by a usually palatalized suffix -f- of uncertain origin that is added after the verb root. This -f- assimilates after a root-final b to leave just a palatal b or f, as seen in marbaid and con·tibi.
The future stem is used to form the conditional tense (called “secondary future” in some sources including Thurneysen and Strachan) as well as the future itself.
See Category:Old Irish f future verbs for a list of verbs that take the f-future.
There are a few verbs that do not take an f-future even in classes where it is expected, and take another formation.
The f-future in the absolute is scattered in attestation, and virtually no weak verb has even a majority forms attested simultaneously; hence the forms shown below for léicid are constructed on the basis of attested endings.
| 1st sg. | 2nd sg. | 3rd sg. | 1st pl. | 2nd pl. | 3rd pl. | Passive singular | Passive plural | |
|---|---|---|---|---|---|---|---|---|
| Absolute | léicfea | léicfe | léicfid | léicfimmi | léicfithe | léicfit | léicfidir | léicfitir |
| Conjunct | ·léiciub | ·léicfe | ·léicfea | ·léicfem | ·léicfid | ·léicfet | ·léicfider | ·léicfetar |
| Relative | léicfes | léicfimme | léicfite | léicfider | léicfiter, léicfetar |
| 1st sg. | 2nd sg. | 3rd sg. | 1st pl. | 2nd pl. | 3rd pl. | Passive singular | Passive plural |
|---|---|---|---|---|---|---|---|
| ·léicfinn | ·léicfeda | ·léicfed | ·léicfimmis | ·léicfide | ·léicfitis | ·léicfide | ·léicfitis |
The f of the f-future (and, in the first-person singular conjunct, the root-final consonant before the ending -iub) is usually palatalized not only in A II verbs but in A I verbs as well, e.g. ·ainfed (“he will remain”) from anaid and ad·elliub (“I will visit”) from ad·ella. However, there are a few cases of nonpalatalized f as well:
| 1st sg. | 2nd sg. | 3rd sg. | 1st pl. | 2nd pl. | 3rd pl. | Passive singular | Passive plural | |
|---|---|---|---|---|---|---|---|---|
| Absolute | molfait | |||||||
| Conjunct | ·cumsanfa | ·delcfam | ·ucbaid* | |||||
| *With -baid for usual -faid. | ||||||||
No complete paradigm of the deponent conjugation is attested, but many endings can be deduced on the basis of other conjugations. Taking dechraigidir (“to differ”) as an example onto which attested and deduced endings can be added, we can derive the following:
| 1st sg. | 2nd sg. | 3rd sg. | 1st pl. | 2nd pl. | 3rd pl. | Passive singular | Passive plural | |
|---|---|---|---|---|---|---|---|---|
| Absolute | dechraigfer | dechraigfider | dechraigfidir | dechraigfimmir | dechraigfide | dechraigfitir | dechraigfidir | dechraigfitir |
| Conjunct | ·dechraigfer | ·dechraigfider | ·dechraigfedar | ·dechraigfemmar | ·dechraigfid | ·dechraigfetar | ·dechraigfider | ·dechraigfetar |
| Relative | dechraigfes | dechraigfimme | dechraigfite | dechraigfider | dechraigfiter, dechraigfetar |
| 1st sg. | 2nd sg. | 3rd sg. | 1st pl. | 2nd pl. | 3rd pl. | Passive singular | Passive plural |
|---|---|---|---|---|---|---|---|
| ·dechraigfinn | ·dechraigfeda | ·dechraigfed | ·dechraigfimmis | ·dechraigfide | ·dechraigfitis | ·dechraigfide | ·dechraigfitis |
Also in the deponent conjugation there are cases where the f and any preceding consonants are nonpalatalized, for example in molaidir (“to praise”):
| 1st sg. | 2nd sg. | 3rd sg. | 1st pl. | 2nd pl. | 3rd pl. | Passive singular | Passive plural | |
|---|---|---|---|---|---|---|---|---|
| Absolute | molfar | molfaider | molfaidir | molfaimmir | molfaide | molfaitir | molfaidir | molfaitir |
| Conjunct | ·molfar | ·molfaider | ·molfadar | ·molfammar | ·molfaid | ·molfatar | ·molfaider | ·molfatar |
| Relative | molfas | molfaimme | molfaite | molfaider | molfaiter, molfatar |
| 1st sg. | 2nd sg. | 3rd sg. | 1st pl. | 2nd pl. | 3rd pl. | Passive singular | Passive plural |
|---|---|---|---|---|---|---|---|
| ·molfainn | ·molfada | ·molfath* | ·molfaimmis | ·molfaide | ·molfaitis | ·molfaide | ·molfaitis |
| * With -fath for usual -fad. | |||||||