Learn Spanish (Spain): Esto es el libro.

Esto is a neuter pronoun, meaning it doesn't have a specific masculine or feminine gender. It translates to "this thing" in general. We use esto when "this" stands alone as the subject of a sentence, such as when you point at an object and say "This is...". However, if you wanted to attach "this" directly to the noun to say "this book", you would match the masculine gender and use este instead: este libro.

Why do we use es for the verb here?

Es is the form of the verb ser (to be) that means "is". We use it for singular subjects like él (he), ella (she), and also for "it" or "this" (esto). The verb ser is always used when you are identifying what an object is.

How do I know whether to use el or la before libro?

In Spanish, every noun has a grammatical gender, either masculine or feminine. Libro is a masculine noun (many masculine nouns end in -o). Therefore, you must use the masculine singular word for "the", which is el. If you were pointing out a feminine noun, like mesa (table), you would use la: Esto es la mesa.

Can I drop the word el and just say Esto es libro?