-isc- verbs
Many -ire verbs add -isc- in four of the six present-tense forms.
Verbs like capire (to understand), finire (to finish), preferire (to prefer) and pulire (to clean) insert -isc- between stem and ending in io, tu, lui/lei and loro: capisco, capisci, capisce, capiamo, capite, capiscono.
The noi and voi forms never take -isc-: capiamo, capite; finiamo, finite. So the pattern is: -isc- everywhere except noi and voi.
There is no reliable way to guess whether an -ire verb takes -isc- — dormire does not, capire does. Learn each verb with its io form (capire → capisco) and the rest follows.
stem + isc + ending (io, tu, lui/lei, loro); plain endings for noi, voi
Examples
- Capisco l'italiano. I understand Italian.
- Non capisci? Don't you understand?
- Finisco alle cinque. I finish at five o'clock.
- Preferiamo il treno. We prefer the train. (no -isc- with noi)
- Loro puliscono la casa il sabato. They clean the house on Saturdays.
Common mistake
Carrying -isc- into the noi form (capisciamo) — noi and voi stay plain: capiamo, capite.