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"Necesito" is a form of "necesitar", a transitive verb which is often translated as "to need". "Pues" is a conjunction which is often translated as "then". Learn more about the difference between "necesito" and "pues" below.
necesitar(
neh
-
seh
-
see
-
tahr
)A transitive verb is a verb that requires a direct object (e.g., I bought a book.).
1. (to require)
An auxiliary verb, or helper verb, is a conjugated verb that comes before a main verb and determines the main verb's tense, mood, or aspect (e.g., I have gone.).
a. to need
Necesitan salir ya si quieren alcanzar su vuelo.You need to leave now if you want to make your flight.
pues(
pwehs
)A conjunction is a word that connects words, phrases, clauses, or sentences (e.g., The cat and the dog slept.).
a. then
Estoy cansado. - Pues vete a dormir.I am tired. - Go to sleep then.
No sé qué decirte, pues.I don't know what to tell you, then.
2. (emphatic)