ser and estar is correct in many contexts, but there is a difference in nuance. When referring to animate objects, ser is only used to tell about permanent conditions (for example és boig, "he is insane"; és mort, "he is dead.") Things traditionally thought of as permanent conditions also fall under this category, most notably ser casat/da, "to be married", and related terms. Ser is also used with the past participle of some unaccusative verbs such as néixer, which in medieval and dialectal Catalan made their compound tenses with ser. When referring to animate objects, estar is only used to tell about non-permanent conditions (for example estàs molt guapa, "you look good" as in "better than usual.") With fixed prepositional locutions, estar is most often used (for example, està en perill, "he/she/it is in danger"; està a punt, "he/she/it is ready.") When referring to location, ser is used when no time context is given (for example, els llibres són als prestatges, "the books are on the shelves.") When referring to location, estar is used when there is a sense of permanence (for example estic a Barcelona, "I live in Barcelona") or of a concrete time lapse (for example hi vam estar dues hores, "we were there for two hours.") In this case, pronominal particles might be added to the verb to emphasise the sentence (for example, ens hi vam estar dues hores.) Estar is always used with modal adverbs (for example estic bé, "I am all right"). Estar is used to form the present continuous form estar + gerund, although some linguists think this is not a genuinely Catalan form, even though it is found on Medieval literature, for example that of Ausiàs March. Another undoubtedly genuine but perhaps too literary form is ser a + infinitive. Estat is used as the past participle of not only estar but also èsser/ser by many speakers, and this is considered the universal form. However, many other speakers use a traditional regular past participle of èsser/ser: sigut, which is also accepted as standard in Central Catalan, although many linguists and speakers see it as colloquial. Another accepted form is sét, unlike the Valencian form segut, which causes confusion with the past participle of the verb seure, "to sit." This can be summed up in five simple rules: Ser is always used to apply adjectives to inanimate objects except if there is a cause