to: ¿Dónde es la fiesta? = "Where is the party?" ¿Dónde está la discoteca? = "Where is the nightclub?" Words requiring ser Ser is always used when the complement is a noun or pronoun, regardless of whether the speaker intended to express a fundamental essence (though in practice speakers do tend to express this): Él es una persona sucia = "He is a dirty person" Ella es una persona abierta = "She is an open person" Yo soy la víctima = "I am the victim" However, it is not always easy to know what is a noun. For example, pez is a noun meaning "fish", but estar pez is a colloquial expression meaning "not to have a clue" or "to be at sea" at a given activity. Words requiring estar Estar must be used when the complement is bien or mal, no matter what meaning is intended. Este libro está muy bien = Este libro es muy bueno = "This book is very good" (nature) Estoy muy mal = Estoy muy malo = "I am feeling terrible, ill" (state) Total change of meaning with specific adjectives Many adjectives change in meaning entirely depending on the verb used, sometimes meaning almost the opposite. In each case, the meaning which is more of a "nature" goes with ser and the meaning which is more of a "state" goes with estar. Happiness Although "sadness" is expressed straightforwardly with estar triste, "happiness" is a little trickier. The quality of being joyous, lively and happy is expressed with ser alegre. This can describe people, music, colours, etc. Estar alegre expresses the state of being merry, which in practice may sometimes mean "drunk", "tipsy". A person who is fundamentally happy in life is said to ser feliz; indeed la felicidad is that "happiness" for which humans strive. This happiness often turns out to be a transitory state, a person may nevertheless declare yo soy feliz as a statement of optimism that goes beyond the description of today's mood that is expressed by any phrase with estar. As for such moods, they can be expressed with estar feliz. When not a state but a change of state is referred to, the expression is quedar contento or alegrarse: Ella quedó muy contenta cuando yo le dije que ella había ganado = "she was very glad when I told her that she had won"; Yo me alegro de que