each の用法は determiner か pronoun です。

each の意味

each は 2 つ以上から構成される何か(人・物)のグループ内の個々を指します。

We spent five days on the coast and each day we swam in the ocean. (determiner)

determiner の用法

each が伴う noun は可算名詞の単数形か “one” です。

単数扱い以外はあり得ません。※informal を除く

eg. Each weekend, they would work on the house.
eg. The houses were made of grey stones and mud bricks, and each one had a flat roof of pressed earth laid over mats.

次の条件の時は each of を使用します。

  • 単数形の nooun が他の determiner を伴う時
  • 複数形の noun の時
  • 複数形の代名詞の時(us, you, them)
A: There are meetings every month to plan events.
B: Do you go to each of the meetings?
They were trying to decide where to go on holiday but the problem was that each of them wanted to go to different places.
each of + 複数形が主語で使われる時は動詞の人称は三人称単数になります。

Each of the buildings is surrounded by high metal fencing.

Each of the horses has won major international races.

但し、informal な会話では複数扱いになる場合もあります。

each one of は each の持つグループの中の個々人を強調する時に使います。each one of も単数扱いです。

Each one of the passport control desks now has a camera as well as a computer.

each referring to the subject

each が節の主語を指す事ができます。この時は adv の位置に each を配置します。

We each agreed to help by contributing some money towards the cost.

We would each say a poem or sing a song.

Have you each signed the contract?

Husband and wife are each entitled to invest up to the maximum of£40,000.

Each + pronouns and possesives

he/she/women/men と男女をマナーとして区別したくない時に each + 可算名詞の単数形を後で複数形の代名詞で受ける用法です。

Each person who joins the gym gets a free bag and they get a pass to bring a friend for a free visit. (Each person and they avoids saying each man and woman and he, she.)

Each member of the community should take pride in their local environment.

pronoun の用法

明示的には書かれていませんが each が指すものが明らかな時に pronoun として使えます。

There were four rooms, each with wonderful views of the garden. (pronoun)

この文章の , each~は four rooms と同格関係になっており、 four rooms の説明をしています。

その他

なぜ、限定詞 + noun が文頭に来れるのかが説明できません。

Each weekend, they would work on the house.

これは名詞の副詞的用法(副詞的目的格)と言うもので例えば this morning が副詞的に文中に配置される用法です。時間、距離、数量、様態(姿、形、方法など)を表す名詞はそれ単体で副詞として扱えます。