Learn Spanish (Latin America): El abuelo tiene sueño.

In English, we use "to be" plus an adjective for physical states, like being hungry, thirsty, or sleepy. In Spanish, you use tener (to have) plus a noun. So instead of saying "The grandfather is sleepy", Spanish literally says "The grandfather has sleepiness" (El abuelo tiene sueño).

Doesn't the word sueño also mean "dream"?

Yes, it does! The noun sueño can mean either "dream" or "sleep" depending on the context. When paired with tener to describe how someone is feeling, like in tiene sueño, it always refers to feeling sleepy.

If we were talking about the grandmother (la abuela), would sueño change to sueña?

No, it stays exactly the same: La abuela tiene sueño. This is because sueño is a noun (meaning "sleepiness"), not an adjective describing the grandparent. Because it is a noun, its spelling doesn't change to match the person who "has" it.

Why doesn't the word El have an accent mark here?

In Spanish, el (without an accent) means "the", as in el abuelo (the grandfather). If it had an accent mark (él), it would mean the pronoun "he".