sedeo

Sedeo, sedere, sedi, sessum is second conjugation with a short one-syllable perfect, sedi, which sits uncomfortably close to the present sedet - sedet is "he sits", sedit is "he sat". That single vowel is the whole difference, and it catches people out in every chapter of Livy.

The verb is intransitive: you sit, you do not sit somebody. Beyond posture it means to stay put, to be encamped, to be in session, and of a place simply to lie or be situated. The compounds shift the vowel to -ideo: assideo, obsideo, possideo, praesideo, all with perfects in -sedi. Do not confuse it with sedo, sedare (first conjugation), "to calm, settle". English sedentary, session, siege, preside, reside, assiduous and sediment all descend from it.