それとも vs または vs あるいは vs もしくは

Or; or else, when offering an alternative

それとも connects two alternatives, most often in questions, meaning 'or'. It comes after a complete sentence or clause, and can also stand between two noun phrases as in the third example. It is used in spoken and written Japanese when offering a choice.

1. あなたは電車でんしゃで行いきますか、それとも車くるまで行いきますか。

   Do you go by train or by car?

2. あなたはバスで通学するのですか、それとも電車でですか。

   Do you go to school by bus or by train?

Used to link choices: one option or the other; either of two alternatives

または connects two alternatives, meaning one or the other applies. It follows nouns or clauses, often after a か-marked first option, and has a formal tone common in legal, business, and written language.

1. お支払しはらいはクレジットカードまたは銀行ぎんこう振込ふりこみでお願ねがいします。

   Please pay by credit card or bank transfer.

2. 申込書は郵送または窓口で提出してください。

   Please submit the application form by mail or at the counter.

or; either...or; as another option; maybe

あるいは connects two alternatives, meaning "or" between words, phrases, or clauses, and can also suggest a possibility like "perhaps." It is a formal conjunction, common in written or polite language, and simply follows whatever element it links without changing its form.

1. その木きは実みがならないかあるいは小ちいさな実みしかつけない。

   The trees are barren or bear only small fruit.

2. １００年あるいは５０年前事情はどうであったか私は知らない。

   I don't know how things were a hundred or fifty years ago.

Or; either ~ or (formal written)

もしくは connects two nouns or phrases to mean 'or', presenting alternatives. It follows nouns directly, often after a comma, and can also link longer clauses. It has a formal, written tone, so it suits official documents and polite questions rather than casual speech.

1. 彼かれは英語えいご、フランス語ご、もしくはドイツ語ごを話はなせますか？

   Does he speak English, French or German?

2. ７０年もしくは８０年が人間の普通の寿命期間である。

   Seventy or eighty years is the normal span of a man's life.