In English, articles help identify a noun.

• a / an — one item, not specific
• the — a specific item

Examples:

a book / an apple / the book

Sometimes English nouns appear without an article. This is called the zero article. This usually happens when speaking about things in a general sense, or about things that cannot be counted individually.

• Birds fly.
• I like music.

Japanese nouns usually appear without articles.

犬いぬがいる
— a dog is here
— the dog is here

The exact meaning depends on the situation.

Japanese often clarifies nouns using demonstratives, counters, or descriptive phrases.

• この本ほん — this book
• その犬いぬ — that dog
• あの店みせ — that shop over there
• それです — that's it / that's the one

Japanese can also specify a noun using quantity.

　I bought a book.
　本ほんを 一冊いっさつ 買かった。

Context also plays an important role.

本ほんを買かった
　I bought a book
　I bought the book
　I bought books

These meanings are understood from the context of the conversation.

In everyday English, some nouns that are normally uncountable can become countable when referring to a serving.

• I drank beer. — general substance
• I drank a beer. — one glass or bottle of beer

In everyday conversation, words such as “glass of” are often omitted.

I drank a beer.
ビールを（一杯いっぱい）飲のんだ。

In some English exams in Japan, students may be expected to write “I drank beer,” because beer is usually taught as an uncountable noun.

So everyday English and school grammar do not always match perfectly.