no es capaz de

is not able to

→ no
phrase Common #4,826
is not able to Used with an infinitive to say that someone cannot or is unable to do something. The verb ser changes according to the subject, as in no soy capaz de, no fui capaz de, and no seremos capaces de.
SP: No es capaz de hacerlo sin ayuda.
EN: He is not able to do it without help.

Él no es capaz de abrir la boca delante de su padre.

He can't open his mouth in front of his father.

Tom no es capaz de encontrar su reloj.

Tom can't find his watch.

No es capaz de hacer nada solo.

He/She is incapable of doing anything on his/her own.

No te burles de él porque no es capaz de escribir su nombre.

Don't make fun of him because he can't write his name.

Él no es capaz de escribir su propio nombre.

He is unable to write his own name.

Ella no es capaz de distinguir entre el bien y el mal.

She is unable to distinguish between good and evil.

Tom no es capaz de nadar tan rápidamente como Mary.

Tom can't swim as fast as Mary.

No es capaz de controlarlo, señor.

He's not able to control it, sir.

— Akira (1988)

Que esta no es capaz de tener la boca cerrada.

She's incapable of keeping her mouth shut.

— Todo sobre mi madre (1999)

Tom no es capaz de confesar a Mary sus sentimientos reales.

Tom isn't able to confess his true feelings to Mary.

No es capaz de guardar un secreto.

He/She can't keep a secret.

Él no es capaz de comprarse un coche.

He can't afford to buy himself a car.

Ella no es capaz de amar a ningún hombre.

She is incapable of loving any man.

No es capaz de amar, querrá decir.

It means he/she is incapable of love.

— La princesa prometida (1987)

Él no es capaz de ver la cuestión desde mi punto de vista.

He is not able to see the issue from my point of view.

Ella no es capaz de hacer esa tarea.

She is not capable of doing that task.

Tom no es capaz de conducir un coche.

Tom is not able to drive a car.

No es capaz de decir una mentira.

He/She is incapable of telling a lie.