Learn Hardcore Japanese: ibento ni sankasuru to, tiisana keihin wo moraeru kamo siremasen. - If you take part in the event, you might get a small prize.

イベントで参加する – sounds wrong; で marks the place where an action happens, but the action itself is “participate,” and “event” is the target of participation, not just a physical location.
イベントを参加する – incorrect; 参加する is normally intransitive in Japanese, so it doesn’t take を for the thing you join.

So: with 参加する, use に for “in/at (the event)”.

What does と mean in 参加すると? Is it “and” or something else?

Here と is not “and.” It’s the conditional と, meaning “when/if”:

イベントに参加すると、…
“When/If you participate in the event, …”

This と often expresses:

a natural, automatic result:
春になると、暖かくなります。– When spring comes, it gets warm.
things that always happen in that situation.

So 参加すると suggests: “Whenever / if you (happen to) participate, the following result occurs.”

It is different from:

quotation と (e.g., 彼は「行く」と言った – He said “I’ll go”).

Here it’s purely the conditional “if/when”.

Why is it 参加する (plain dictionary form) and not 参加します before と? Is it okay to mix plain and polite in one sentence?

Before と (as a conditional), the verb is put in plain form:

Verb (plain) + と + result clause
行くと / 行ったと / 行かないと, etc.

So:

✗ イベントに参加しますと – unnatural
✓ イベントに参加すると – correct

About politeness:
Japanese politeness is mainly decided by the final verb of the sentence. Inside the sentence (in subordinate clauses), plain forms are common even in polite speech.

Here the final part …かもしれません is polite, so the overall sentence is polite, even though the first verb is plain:

イベントに参加すると、…かもしれません。 – perfectly natural polite Japanese.

What is もらえる exactly? How is it different from もらう?

もらえる is the potential form of もらう.

もらう – “to receive, to get”
もらえる – “to be able to receive / can receive / might receive”

Formation (for もらう – a godan verb):

もらう → change う to the え-row → もらえ → add る = もらえる

Difference in nuance:

景品をもらう – (you) receive the prize (simple fact).
景品をもらえる – (you) can receive the prize / it’s possible to receive it.

In this sentence, “you might be able to get a small prize” is a natural nuance, especially combined with かもしれません.

What does かもしれません mean, and how strong is it? Is it like “probably”?

かもしれません means “might / may / it’s possible that …”
It expresses uncertainty and is usually thought of as weaker than “probably.”

Rough feeling:

かもしれません – “maybe, possibly” (could be, could not be)
でしょう – often closer to “probably” / “I think so.”

So:

景品をもらえるかもしれません
→ “You might be able to get a small prize.”
(They are not sure it will happen.)

It’s the polite form of かもしれない.

Why is it split as かもしれません? Can I use かも by itself?

Historically this comes from:

かも知れません (知れません = “cannot be known”)

In modern Japanese, it’s almost always written as:

かもしれません (polite)
かもしれない (plain)

Many people pronounce it with a slight break: ka mo shirena–sen, which you see written as かも　しれません in teaching material.

Can かも stand alone?

In casual speech, yes:
- 行くかも。– I might go.
- 雨かもね。– It might rain.
In polite speech, you normally use the full form:
- 行くかもしれません。
- 雨が降るかもしれません。

So in this sentence, the “proper” full form is もらえるかもしれません.

What’s the difference between 小さな and 小さい in 小さな景品?

Both relate to “small,” but they’re used differently grammatically:

小さい – a regular い-adjective
- 小さい景品 – a small prize
- 景品は小さいです – The prize is small.
小さな – a prenominal form (連体詞) used only directly before a noun
- 小さな景品 – a small prize
- ✗ 景品は小さなです – incorrect

Nuance:

小さい – neutral, everyday.
小さな – often sounds a bit more literary, slightly softer or more descriptive. You’ll see it in writing, narration, set phrases (小さな村, 小さな声, etc.).

In this sentence, 小さな景品 could easily be 小さい景品 with almost no change in meaning; 小さな just feels a bit more “written” or stylistic.

What exactly does 景品 mean? How is it different from 賞品, プレゼント, or おまけ?

All can be translated as “prize/gift,” but they’re used in different situations:

景品（けいひん）
- Prizes or small gifts given out at events, campaigns, lotteries, promotions.
- Often small or promotional items.
- Example: 抽選で景品が当たります。– You can win a prize in the lottery.
賞品（しょうひん）
- A prize in a contest/competition, often something valuable.
- Example: 優勝者には賞品が贈られます。– A prize is awarded to the winner.
プレゼント
- A general present/gift (birthday present, Christmas gift, etc.).
おまけ
- A free extra that comes with a purchase, like a free toy with candy, or something a shopkeeper adds.
- Example: お菓子を買うと、おまけがついてきます。– If you buy the sweets, a free extra comes with it.

In the original sentence, 小さな景品 is a small giveaway item you might get for participating.

Why is there no explicit subject like “you” in this sentence?

Japanese often omits the subject when it’s clear from context.

イベントに参加すると、小さな景品をもらえるかもしれません。

From context (a poster, announcement, etc.), it’s naturally understood as:

“If you participate in the event, you might get a small prize.”

Japanese does not need to say あなた (“you”) unless it’s necessary or emphatic. In fact, adding あなた here:

あなたはイベントに参加すると、小さな景品をもらえるかもしれません。

would sound a bit unnatural or overly direct in most real-life contexts.

Could I say イベントに参加したら instead of 参加すると? What’s the difference?

Yes, you could say:

イベントに参加したら、小さな景品をもらえるかもしれません。

This is also natural. The nuance difference:

〜すると
- Tends to express a regular / natural result that follows whenever that condition is met.
- Often used for general rules, automatic outcomes.
〜したら
- More general “when/if” in time or condition.
- Often feels a bit more event-based (“if it happens that you do X”).

In this sentence, both are fine. 参加すると leans slightly toward “whenever/if you participate, as a rule, you might get a small prize,” but in practical everyday use, the difference is very small here.

Could I say イベントで参加する instead of イベントに参加する?

No, イベントで参加する is not natural.

With 参加する, the typical pattern is:
X に参加する – participate in X

So:

イベントに参加する – participate in the event
会議に参加する – take part in the meeting
チームに参加する – join the team

Using で would suggest the event is just the place where you do some action, not what you are participating in. But 参加する already contains the idea of “joining” that event itself, so に is the correct particle.

Why not just say もらえます instead of もらえるかもしれません? How do these differ in meaning?

The difference is in certainty and nuance:

もらえます – “(you) can get (it).”
- Suggests that the ability/permission is there as a fact.
- イベントに参加すると、小さな景品をもらえます。
  → “If you participate, you can get a small prize.”
  (Sounds more like a clear rule/benefit.)
もらえるかもしれません – “(you) might be able to get (it).”
- Adds uncertainty. Maybe there’s a limited number, or there are conditions.
- イベントに参加すると、小さな景品をもらえるかもしれません。
  → “If you participate, you might be able to get a small prize.”

So もらえます is stronger and more assured; もらえるかもしれません is weaker and more cautious.