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"Necesito" is a form of "necesitar", a transitive verb which is often translated as "to need". "Hay que" is a phrase which is often translated as "one must". Learn more about the difference between "necesito" and "hay que" 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.).
2. (to be necessary)
a. to need
Necesitan salir ya si quieren alcanzar su vuelo.You need to leave now if you want to make your flight.
hay que(
ay
keh
)A phrase is a group of words commonly used together (e.g once upon a time).
1. (general)
b. no direct translation
This refers to an idiomatic word or phrase for which there is no word-for-word translation.
Hay que llenar la solicitud a mano.The application must be filled out by hand.
Hay que trabajar mucho para ser exitoso.You have to work hard to be successful.