Past participles in Dutch are used in perfect tenses, passive constructions, and as adjectives. For regular (weak) verbs, form the past participle by adding ge- to the stem + -t or -d: werken → gewerkt, leven → geleefd. The ‘t kofschip rule determines -t vs. -d: if the final consonant of the stem appears in the word ‘t kofschip (t, k, f, s, ch, p), use -t; otherwise use -d. Koken → stem kook → final k is in kofschip → gekookt.
For strong (irregular) verbs, the past participle uses ge- + ablaut stem + -en: rijden → gereden, schrijven → geschreven, komen → gekomen, gaan → gegaan, zijn → geweest. Some verbs have completely irregular participles: doen → gedaan, staan → gestaan, gaan → gegaan. Participles of separable verbs insert ge- between prefix and stem: opbellen → opgebeld, meenemen → meegenomen.
Verbs with inseparable prefixes (be-, ver-, er-, her-, ge-, ont-) do not add ge-: bezoeken → bezocht, vergeten → vergeten, herhalen → herhaald. Verbs ending in -ieren also skip ge-: interesseren → geïnteresseerd (exception — this one takes ge-). Recognizing whether a verb is separable or inseparable is therefore essential for forming the correct past participle — another reason to always learn verbs with their prefix type.