crazy. The expression como una cabra (with the implied loco omitted) is used with estar to mean "mad as a hatter", "crazy as a loon". Ser como una cabra would literally mean, "to be like a goat". Ser is used with adjectives of fundamental belief, nationality, sex, intelligence, etc. The use of estar with francés ("French") would sound quite odd to native Spanish speakers, as though it meant, "to feel a bit French". Similarly, no estar católico does not mean, "to no longer be Catholic", but is a colloquial expression meaning "to feel under the weather". It is often stated that the difference between the two verbs corresponds to "permanent" versus "temporary", but it is more accurate to describe the distinction as one of "essential nature" versus "state or condition". The "essential nature" of things does sometimes change, and this is reflected in the language. For example, someone who had been depressed for a prolonged period, and then had a life changing experience like a new career or long-term relationship, might say ahora yo soy feliz, meaning, "now I am happy". Specific constructions requiring ser A special use of ser, which expresses neither a nature nor a state but an action, is the formation of the passive voice: Ellos han sido asesinados = "They have been murdered" Tú serás juzgada = "You will be judged" Specific constructions requiring estar Past participles Estar is usually used with adjectives that derive from past participles of verbs since the use of ser would sound like a verb in the passive voice. Such adjectives in any case generally refer to states: La frontera está cerrada = "The border is closed" Estoy casado = "I am married" (Soy casado is also possible; "I am single", "I am widowed", etc. can use ser or estar as well) A special example of this tendency is what happens with words indicating prohibition and suchlike. If an adjective not deriving from a verb were used, then the meaning would definitely require ser. To say the same thing with a past participle, estar (or quedar) is required, in order to differentiate it from the use of ser with a past participle implying an action expressed in the passive voice: Es ilegal fumar en este vuelo = "It is illegal to smoke on this flight" (straightforward case of ser) Está prohibido fumar en este vuelo = "It is prohibited to smoke