Not "I were at home." — say "I was at home.". I の過去の形は were ではなく was です。
やってみよう: Last weekend the market ___ very busy. (was / were / is) 答え: was — The market = it なので、were ではなく was を使います。（「Is」は現在形で、「last weekend」から過去だとわかります。）したがって: the market was busy。
You / we / they: were
you, we, または they のときは were を使います。
You were late.
We were happy.
They were at school.
Not "They was at school." — say "They were at school.". they のときは were を使います。was は I, he, she, it のときだけです。
やってみよう: Last weekend, Amina and Hiroshi ___ at Magaff Library. (were / was / are) 答え: were — Amina and Hiroshi ＝ they なので、was ではなく were になります: They were at Magaff Library。
was それとも were？
選ぶ前に「だれ？」と考えてみましょう。I/he/she/it → was、you/we/they → were です。
He was here. / They were here.
I was tired. / We were tired.
Not "He were here. / They was here." — say "He was here. / They were here.". だれのことかで決まります。I/he/she/it は was、you/we/they は were です。
やってみよう: Mei: Was everyone at the park on Saturday? Lars: No. I ___ there, but my friends ___ at the gym! Lars の言葉を完成させてください。 (was … were / were … was / was … was) 答え: was … were — Lars は I と言います → was。His friends ＝ they → were。だれかによってそれぞれ決まります。
否定文: wasn't / weren't
was や were の後ろに not を足します: wasn't（I/he/she/it）、weren't（you/we/they）。
I wasn't hungry.
He wasn't there.
They weren't happy.
Not "I not was hungry." — say "I wasn't hungry.". not は was の前ではなく後ろにつきます。
やってみよう: She ___ at home last night. (wasn't / weren't / not was) 答え: wasn't — She には was を使うので、否定は（weren't ではなく）wasn't になり、not は後ろにつきます: She wasn't at home。
疑問文: Was / Were を先に
たずねるときは、Was か Were を人の前に置きます。
Was she at home?
Were you late?
Was it cold?
Not "You were late? (asking)" — say "Were you late?". 疑問文では were が先に来て、そのあとに人が続きます。
やってみよう: Camila: The children are inside now, and they look very cold. Hiroshi: ___ outside all morning? Hiroshi の質問を完成させてください。 (Were they / They were / They was) 答え: Were they — たずねるときは Were が先に来て、人はそのあとに続きます。1つの答えは人を先に置いていて、これは質問ではなく、相手に何かを伝えるときの言い方です。もう1つは was を使っていますが、これは I, he, she, it のときの形で、they には使いません。
やってみよう: Remember: who is it? Mei ___ at the cooking class. (was / were / are) 答え: was — Mei ＝ she → was。（これが基本の選択です: I/he/she/it → was、you/we/they → were。）
よくある間違いは？
間違い
正しい
理由
I were at home.
I was at home.
I の過去の形は were ではなく was です。
They was at school.
They were at school.
they のときは were を使います。was は I, he, she, it のときだけです。
He were here. / They was here.
He was here. / They were here.
だれのことかで決まります。I/he/she/it は was、you/we/they は were です。