When you start exploring intermediate Japanese grammar, you'll notice two important phrases: ことができる and ことがある. These phrases are useful when talking about what you can do and your past experiences. At first, they may look similar, but they have different meanings and levels of formality. Let’s make it simpler to understand.

ことができる (koto ga dekiru)

1. What It Means:

   • This phrase is used to show capability. It means someone can do something, like a skill or ability. For example:
     • 日本語を話すことができる。(Nihongo o hanasu koto ga dekiru.) - "I can speak Japanese."
   • This shows that you have the ability to do something.

2. Formality:

   • How formal you are can change how you use ことができる.
   • In formal situations, use ことができます. This is better for business or formal talks, like giving a presentation.
   • In casual settings with friends, you can keep it light. Just say things like 頑張ればできる (ganbareba dekiru), which means "If you try hard, you can do it."

ことがある (koto ga aru)

1. What It Means:

   • In contrast, ことがある is used to talk about experiences or things that have happened. For example:
     • 日本に行ったことがある。(Nihon ni itta koto ga aru.) - "I have been to Japan."
   • This tells us that you experienced something in the past.

2. Formality:

   • Just like with ことができる, you can change the formality with ことがある.
   • In a formal setting, you might say ことがあります (koto ga arimasu) to show respect, like during a job interview.
   • With friends, you could say 行ったことある？(Itta koto aru?) - "Have you been?"

Key Differences

• Focus:
  • ことができる is about ability, while ことがある is about experiences.
• Usage Examples:
  • If you want to share a skill:
    • できる: ギターが弾ける。(Gitaa ga hikeru.) - "I can play the guitar."
  • If you're talking about past events:
    • ある: コンサートに行ったことがある。(Konsaato ni itta koto ga aru.) - "I have been to a concert."

Summary of Tips

1. Use ことができる when you want to talk about what you can do or your abilities.
2. Use ことがある to tell about experiences or things that happened before.
3. Change the formality based on who you are talking to. Use ことができます and ことがあります in formal talks, and keep it casual with friends.

Knowing the differences between these phrases will help you speak and write in Japanese more naturally. So practice using them in your conversations and enjoy learning this beautiful language!