Если будет скидка, я куплю ещё один билет на концерт.

In Russian, when you are talking about a real future possibility, you normally use the future tense after если.

So:

• Если будет скидка = If there is / if there will be a discount
• Если есть скидка = If there is a discount in a more present, current sense

This is different from English, where we usually say If there is a discount, I'll buy... and avoid will after if. Russian does not follow that rule, so если + future is completely normal.

Будет is singular because the subject is скидка, which is singular feminine.

• скидка = discount
• будет = will be (singular)

If the noun were plural, you would use будут:

• Если будут скидки... = If there are discounts...

So the verb agrees with the noun that follows it.

It is in the nominative because скидка is the grammatical subject of будет.

In Если будет скидка:

• будет = will be
• скидка = the thing that will exist / happen

That makes скидка the subject, so nominative is used.

Куплю is the perfective future of купить, and it means I will buy as a completed action.

Russian has two common ways to talk about the future:

1. Perfective future: куплю

   • focuses on a single completed result
   • I will buy

2. Imperfective future: буду покупать

   • focuses more on process, repetition, or ongoing action
   • I will be buying / I will buy regularly

Here, the speaker means one definite completed action: buying one ticket. So куплю is the natural choice.

These are aspect partners:

• купить = perfective, a completed purchase
• покупать = imperfective, process/habit/repetition

In this sentence, the speaker means one future completed act of buying, so купить → куплю is used.

Compare:

• Я куплю билет. = I will buy the ticket.
• Я буду покупать билеты онлайн. = I will be buying tickets online / I will buy tickets online regularly.

Ещё один means one more or another.

So:

• один билет = one ticket
• ещё один билет = one more ticket / another ticket

In this sentence, it suggests the speaker already has, plans to get, or is considering one ticket, and would buy an additional one if there is a discount.

A useful distinction:

• ещё = still / yet / more, depending on context
• ещё один = one more, another

In Russian, the standard expression is билет на + event.

So you say:

• билет на концерт = ticket to/for a concert
• билет на спектакль = ticket to/for a play
• билет на матч = ticket to/for a match

Russian uses на because the ticket is for an event.
You would not normally say билет в концерт.

It is in the accusative case because it follows на in the expression билет на концерт.

However, концерт is an inanimate masculine noun, and for inanimate masculine nouns, the accusative looks the same as the nominative.

So:

• nominative: концерт
• accusative: концерт

That is why the form does not change.

Yes, often it can be omitted, because the verb form куплю already tells you the subject is I.

So both are possible:

• Если будет скидка, я куплю ещё один билет на концерт.
• Если будет скидка, куплю ещё один билет на концерт.

Including я can make the subject a little clearer or more emphatic. Omitting it can sound slightly more natural in conversation, depending on context.

Because this sentence has a subordinate clause introduced by если:

• Если будет скидка = if there is a discount
• я куплю ещё один билет на концерт = I will buy another ticket to the concert

Russian normally separates this kind of if-clause from the main clause with a comma.

So the comma here is standard and necessary.

Yes. Russian word order is flexible, though the neutral version here is very natural:

• Если будет скидка, я куплю ещё один билет на концерт.

You could also say:

• Я куплю ещё один билет на концерт, если будет скидка.

Both mean the same thing. The difference is mostly in emphasis:

• starting with Если будет скидка... foregrounds the condition
• putting it at the end makes the main action come first

Not exactly, because they are related but not identical.

• скидка = discount, price reduction
• распродажа = sale, sales event

So:

• Если будет скидка... = If there is a discount...
• Если будет распродажа... = If there is a sale...

Both can work, but they do not mean precisely the same thing.

This is one of the common differences between English and Russian grammar.

In English, after if, we usually use the present tense to talk about the future:

• If there is a discount, I’ll buy...

In Russian, after если, you normally use the tense that matches the real meaning:

• present meaning: Если есть скидка...
• future meaning: Если будет скидка...

So Russian is more literal here: if the discount is in the future, the verb is in the future too.