what is the difference between bienvenidos and la bienvenida?
In one document, it reads, Bienvenidos al Nuevo ano escolar 2009-2010. In another, it reads La PTA da la bien venida al nuevo ano escolar. Which is correct and why?
Welcome to the new SpanishDict.com, Nancy.
First, please do not leave the tilde off the ñ in año. The word ano means "anus."
Bienvenidos and dar la bienvenida mean practically the same thing, and both are correct. (You spelled bienvenida correctly in your title, but made it two words your post.)
Bienvenido is an adjective, and as such is declined to agree in gender and number with the noun it describes. Since it refers to everybody (understood here), it is masculine plural, "bienvenidos." If it referred to one masculine (or unspecified gender) entity, it would have been "bienvenido," one feminine entity, "bienvenida," multiple feminine entities, "bienvenidas."
La bienvenida is a noun, and this expression, "dar la bienvenida," means "to give (extend) a welcome," or simply, to welcome.
In the first phrase, "Bienvenidos" is used because it is declaring that everyone is
"welcome(d)" (adjective) to the new school year. In the sentence that follows, the PTA "extends a welcome" (verb/direct object) to the new school year.
Side note: Although it is not impossible or strange to welcome the new school year, it seems like what they were trying to say is, The PTA welcomes you all to the new school year, and not,
The PTA extends a welcome to the new school year. If that is the case, then they need to say,
La PTA les da la bienvenida al nuevo año escolar.
Bienvenidos can be regarded as "Sean bienvenidos" (be welcome)