to form many of the compound tenses of the language. There are regular endings for the past participle, based on the conjugation class (see below). There are, however, many irregular forms as not all verbs follow the pattern, particularly the -ere verbs. Some of the more common irregular past participles include: essere (to be) → stato (same for stare); fare (to do, to make) → fatto; dire (to say, to tell) → detto; aprire (to open) → aperto; chiedere (to ask) → chiesto; chiudere (to close) → chiuso; leggere (to read) → letto; mettere (to put) → messo; perdere (to lose) → perso; prendere (to take, to get) → preso; rispondere (to answer) → risposto; scrivere (to write) → scritto; vedere (to see) → visto. For the intransitive verbs taking essere, the past participle always agrees with the subject—that is, it follows the usual adjective agreement rules: egli è partito; ella è partita. This is also true for reflexive verbs, the impersonal si construction (which requires any adjectives that refer to it to be in the masculine plural: Si è sempre stanchi alla fine della giornata – One is always tired at the end of the day), and the passive voice, which also use essere (Queste mele sono state comprate da loro – These apples have been bought by them, against Essi hanno comprato queste mele – They bought these apples). The past participle when used with avere never changes to agree with the subject. It must agree with the object, though, in sentences where this is expressed by a third person clitic pronoun (e.g. Hai mangiato la mela? – Sì, l'ho mangiata (Have you eaten the apple? – Yes, I have eaten it)). When the object is expressed by a first or second person clitic pronoun instead, the agreement is optional: Maria! Ti ha chiamato / chiamata Giovanni? – No, non mi ha chiamato / chiamata (Maria! Has Giovanni called you? – No, he has not). In all the other cases where the object is not expressed by a clitic pronoun, the agreement with the object is obsolescent in modern Italian (but still correct): La storia che avete raccontata (obsolete) / raccontato non mi convince (The story you told does not convince me); or compare Manzoni's Lucia aveva avute due buone ragioni with the more modern Lucia aveva avuto due buone ragioni (Lucia had had two good reasons). Tense