Irregular conjugation for verbs with the ending -essen: loss of -s in the second singular form of Present Indicative ("du isst/ißt"). Replacement of -e- in the stem of Present tense with -i- for the second and third person singular form of Present tense and singular form of Imperative , and with -a- for Preterite ("ich aß") and -e- in Past Participle ("gegessen").