For size:
* Pequeño: This is the most common antonym for "grande" when referring to physical size. It means "small".
For importance:
* Pequeño: This can also be used for importance, but it might sound a bit informal.
* Menor: This means "smaller" or "less important" and is more formal than "pequeño" when talking about importance.
* Insignificante: This means "insignificant" and is a strong antonym for "grande" in terms of importance.
For quantity:
* Poco: This means "little" or "small amount" and is the most common antonym for "grande" when referring to quantity.
* Escaso: This means "scarce" or "limited" and is a stronger antonym than "poco".
It's important to consider the specific context to choose the most appropriate antonym.