1. Something does not exist where it should
Falta seguridad en este barrio.
There is a lack of security in this neighborhood.
I am $3 short of buying the book I need.
Me faltan 3 dólares para comprar el libro que necesito
2. To miss an important obligation
3. When something is missing from where it usually is
Me falta un libro en el estante
I'm missing a book on the shelf
4. Failure to fulfil a promise or complete what is expected
He promised to call me yesterday, but he broke his word.
Me prometió que me llamaría ayer, pero faltó a su palabra.
5. When something could improve something else if it was there
The soup is lacking salt (to the soup salt is missing).
1. hacer falta = to be necessary
a. Para dominar un arte, hace falta esfuerzo y dedicación.
To master an art, hard work and dedication are needed/necessary.