Learn Spanish (Latin America): Arreglaba los lavaplatos cuando ella llegó. - I was repairing the dishwashers when she arrived.

Lavaplatos (dishwasher) is a compound noun made by combining a verb (lava) and a plural noun (platos). In Spanish, compound words that follow this verb + plural noun structure stay exactly the same in both singular and plural forms. To show that there is more than one, you simply change the article: el lavaplatos (the dishwasher) becomes los lavaplatos (the dishwashers).

Are all compound nouns like lavaplatos masculine?

Yes, the vast majority of compound nouns formed by combining a verb and a noun are masculine. That is why it takes the masculine plural article los in this sentence. Other common examples you might encounter are el abrelatas (the can opener) and el rascacielos (the skyscraper).

Why does this sentence use the imperfect tense (arreglaba) and then the preterite tense (llegó)?

This sentence highlights a very common way the two past tenses interact. The imperfect tense (arreglaba) is used to set the scene and describe an ongoing background action ("I was repairing"). The preterite tense (llegó) is used for the sudden, completed event ("she arrived") that

Since arreglaba can also mean "he/she was repairing", how do we know the speaker means "I was repairing"?