To imply "but" when should I use "а" and when should I use "но"?

Question

I want to imply but

Now, a can mean both and and but

And, но also means but

So, when should I use a and when should I use но?

Answer 1

• 'а' can be used:

  • to juxtapose contrasting statements referring to the same subject category (with the meaning of 'and' or 'while'). The test here is that you can easily swap the statements without changing the meaning:

    Васе семь лет, а Диме - восемь. --- Vasya is seven and/while Dima is eight.

    Слон большой, а мышь - маленькая. --- The elephant is big and/while the mouse is small.

    Мы уезжаем в понедельник, а возвращаемся в пятницу. --- We depart on Monday and return on Friday.

  • to join statements with a one-way logical connection between them (the second statement implies the first one, but not vice versa). Here, 'а' is interchangeable with 'but'. You can test this case by trying to replace 'but' with 'however'.

    Жить хорошо, а/но хорошо жить - еще лучше. --- Life is good and/but/however good life is even better.

    Если ты ей не позвонишь, то она обидится, а/но это совсем не то, чего тебе бы хотелось. --- If you don't call her, she'll be offended, but/however that's not what you'd want.

• 'но' always means 'but/however', joining contrasting statements that refer to different subject categories and do not imply each other:

  Вася и Дима учатся в одном классе, но Дима старше. -- Vasya and Dima are classmates, but/however Dima is older.

  Хотел вчера дописать рассказ, но не смог. --- Wanted to finish the tale yesterday, but couldn't.