kekkon no koto wo hanasimasita.

Here, の links 結婚 to こと.

• 結婚 = marriage / getting married
• こと = matter / thing / topic

So 結婚のこと means something like:

• the matter of marriage
• things about marriage
• the topic of getting married

This の works a bit like about or a possessive/linking marker in English, depending on context.

In this sentence, こと does not mean a concrete thing you can touch. It means a matter, issue, or topic.

So 結婚のこと means:

• marriage matters
• things related to marriage
• the subject of marriage

This is a very common use of こと in Japanese. It often makes an idea sound broader or more abstract.

For example:

• 仕事のこと = things about work
• 将来のこと = things about the future
• 自分のこと = things about oneself

Because 話す usually does not take a bare noun like 結婚 directly as its object in this way.

結婚を話しました sounds unnatural.

Japanese usually says one of these:

• 結婚のことを話しました = talked about marriage
• 結婚について話しました = talked about marriage
• 結婚の話をしました = had a conversation about marriage / talked about marriage

So のこと helps turn 結婚 into a natural topic of discussion.

In this sentence, を marks what was talked about: 結婚のこと.

With 話す, Japanese can use different patterns, and that can confuse learners. Common ones are:

• A について 話す = talk about A
• A のことを 話す = talk about A
• A と 話す = talk with A
• A に 話す = speak to A / tell A

So here:

• 結婚のことを話しました = talked about marriage

The を is not marking a person being spoken to. It marks the content/topic.

It is functioning as a noun here.

結婚 by itself is a noun meaning marriage.
To say to marry / to get married, Japanese usually uses:

• 結婚する

Examples:

• 結婚しました = got married
• 結婚したいです = want to get married

But in 結婚のことを話しました, 結婚 is a noun inside a noun phrase.

Because the sentence is talking about something that already happened: talked.

• 話します = talk / will talk
• 話しました = talked

So the past form simply shows that the conversation happened in the past.

Also, 話しました is the polite form.
The plain form would be:

• 話した

Yes. That is very natural.

• 結婚のことを話しました
• 結婚について話しました

Both can mean talked about marriage.

A small nuance:

• 〜について sounds a bit more direct and explicit as about/regarding
• 〜のこと can sound a little more personal, familiar, or broad depending on context

In many everyday situations, both are fine.

Both are natural, and both often translate as talked about marriage, but there is a slight nuance.

• 結婚のことを話しました
  = talked about matters related to marriage / talked about marriage as a topic

• 結婚の話をしました
  = had a talk/conversation about marriage

話 means talk/story/conversation, while こと means matter/thing/topic.

So:

• 結婚のこと focuses more on the subject matter
• 結婚の話 focuses a bit more on the conversation itself or the topic as a discussion

In many cases, the difference is small.

Because Japanese often omits the subject when it is clear from context.

So even without 私は, the sentence is complete and natural.

Depending on context, it could mean:

• I talked about marriage.
• We talked about marriage.
• He talked about marriage.

Japanese often leaves this unstated if the listener already knows who is being talked about.

The structure is:

• 結婚のこと = the topic/content being talked about
• を = object marker
• 話しました = talked

So literally, it is something like:

• marriage-related matters + object marker + talked

Japanese usually puts the verb at the end, so this is a normal sentence pattern.

Yes, depending on the pattern and context.

For example:

• 友だちと話す = talk with a friend
• 先生に話す = tell/speak to the teacher
• 日本語を話す = speak Japanese
• 結婚のことを話す = talk about marriage

So learners often need to focus on the particles and the overall pattern, not just the dictionary meaning talk.

It is polite, but not especially stiff or highly formal.

• 話しました is polite everyday Japanese
• It is appropriate in normal conversation, class, work, and many general situations

A casual version would be:

• 結婚のことを話した。

So the sentence is best described as polite standard Japanese.