La respuesta rápida

Usa a/an con un sustantivo contable singular, some en frases afirmativas con sustantivos plurales o incontables, y any en preguntas y frases negativas. Se dice Do you have any apples?, no Do you have some apples?

La regla

Los sustantivos contables (countable) se pueden contar y tienen forma plural: one apple, two apples. Los sustantivos incontables (uncountable) no tienen forma plural y no se pueden contar directamente: water, rice, money, advice, information — nunca waters ni informations.

Usa a/an solo con un sustantivo contable singular: an apple. Usa some en frases afirmativas con un sustantivo contable plural o incontable: some apples, some water. Usa any en vez de some en preguntas y frases negativas: Do you have any apples? I don't have any water.

Forma

Ejemplos

• I need an apple.
• She wants some water.
• Do you have any eggs?
• We don't have any milk.
• They need some advice.

Errores frecuentes

• ❌ I need a water. → ✅ I need some water. Water es incontable, así que no puede llevar a/an.
• ❌ Do you have some milk? → ✅ Do you have any milk? Las preguntas normalmente usan any, no some.
• ❌ She gave me some advices. → ✅ She gave me some advice. Advice es incontable y nunca lleva -s.
• ❌ I don't have some time. → ✅ I don't have any time. Las frases negativas normalmente usan any, no some.