How to Say "they exist" in Spanish
The Spanish word for “they exist” is “existen” — A1 level. This is a very common word in everyday Spanish.

Examples
Dicen que las sirenas no existen, pero yo no estoy seguro.
They say that mermaids do not exist, but I'm not sure.
En esta ciudad, existen muchos problemas de tráfico.
In this city, there are many traffic problems.
Ellos solo existen para hacer daño a los demás.
They only exist to harm others.
Subject Agreement
Since 'existen' is the 'they' form, you must use it when the thing that exists is plural: 'Existen tres libros' (Three books exist).
Existir vs. Hay
'Existen' is used when the subject is specified and agrees with the verb. 'Hay' is a special, fixed form that always means 'there is/are,' regardless of whether the thing is singular or plural: 'Hay tres libros' (There are three books).
Mixing Singular and Plural
Mistake: “Existe muchos problemas.”
Correction: Existen muchos problemas. ('Problemas' is plural, so the verb must be 'existen'.)
Related Translations
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