From Proto-Brythonic *hwɨθɨd, from Proto-Celtic *swisdeti (compare Breton c’hwezhañ, Cornish hwytha and Old Irish do·infet (“blow”)), from Proto-Indo-European *sweysd- (“to hiss”) (compare Ancient Greek σίζω (sízō, “I hiss”), Russian свиста́ть (svistátʹ)).
chwythu (first-person singular present chwythaf, not mutable)
| singular | plural | impersonal | ||||||
|---|---|---|---|---|---|---|---|---|
| first | second | third | first | second | third | |||
| present indicative/future | chwythaf | chwythi | chwyth, chwytha | chwythwn | chwythwch | chwythant | chwythir | |
| imperfect (indicative/subjunctive)/ conditional |
chwythwn | chwythit | chwythai | chwythem | chwythech | chwythent | chwythid | |
| preterite | chwythais | chwythaist | chwythodd | chwythasom | chwythasoch | chwythasant | chwythwyd | |
| pluperfect | chwythaswn | chwythasit | chwythasai | chwythasem | chwythasech | chwythasent | chwythasid, chwythesid | |
| present subjunctive | chwythwyf | chwythych | chwytho | chwythom | chwythoch | chwythont | chwyther | |
| imperative | — | chwyth, chwytha | chwythed | chwythwn | chwythwch | chwythent | chwyther | |
| verbal noun | chwythu | |||||||
| verbal adjectives | chwythedig | |||||||
| Inflected colloquial forms | singular | plural | ||||
|---|---|---|---|---|---|---|
| first | second | third | first | second | third | |
| future | chwytha i, chwythaf i | chwythi di | chwythith o/e/hi, chwythiff e/hi | chwythwn ni | chwythwch chi | chwythan nhw |
| conditional | chwythwn i, chwythswn i | chwythet ti, chwythset ti | chwythai fo/fe/hi, chwythsai fo/fe/hi | chwythen ni, chwythsen ni | chwythech chi, chwythsech chi | chwythen nhw, chwythsen nhw |
| preterite | chwythais i, chwythes i | chwythaist ti, chwythest ti | chwythodd o/e/hi | chwython ni | chwythoch chi | chwython nhw |
| imperative | — | chwytha | — | — | chwythwch | — |
| Note: All other forms are periphrastic, as usual in colloquial Welsh. | ||||||