1. conj. (followed by a subjunctive clause) unless
No voy a ver Broadway a no ser que vaya alguna vez a Nueva York. - I'm not going to see Broadway unless I go to New York one day.
No se podía comunicarse con los vecinos, a no ser que hubiera aprendido la lengua. - She couldn't have talked with the neighbours unless she'd learned the language.
Analysis
a
1. prep. to
2. prep. by
3. prep. at
4. prep. ng-lite, Used before words referring to people, pets, or personified objects or places that function as direct objects: personal a.
Lo busca a usted. - He is looking for you.
no
1. adv. no
2. adv. not
3. interj. eh? (used as a tag question, to emphasise what goes before or to request that the listener express an opinion about what has been said)
4. n-m. no
5. n-m. abbreviation of número; no.
ser
1. v. to be (essentially or identified as)
Yo soy de los Estados Unidos. - I am from the United States.
Errar es humano. - To err is human.
2. v. to be (in the passive voice sense)
La guitarra fue tocada. - The guitar was played.
que
1. conj. that
Él dice que está triste. - He says that he is sad.
2. conj. than
Llego más tarde que tú. - I am arriving later than you.