First the context. There are two similar words that cannot be confused:
- Millar → Conjunto de mil unidades. → Set of one thousand elements.
- Millón → Mil millares. → One million.
I've seen a couple of times the word millar used when millón should be used, I think because the former is less used since there are other ways to express its meaning, e.g.:
Millares de personas salieron a las calles
Miles de personas salieron a las calles
Thousands of people marched on the streets.
My question is the following:
Is it advisable to use miles instead of millares to avoid confusion, or is their difference actually understood among Spanish speaking people?