They are spoken words and sentence-ending particles that mean “because“. They are used to give the reason for something.
“もん” is resulting in the phonetic change of “もの“. It is often used to make excuses by kids, but adults also use it among their friends and family members. “もん” is used by both men and women, but “もの“ is used only by women.
“もん“ and “もの“ are interchangeable with “から“ and “ので“, but “もん“ and “もの“ are more emotional way to say.
“だって“ is a conjunction that means “because“ and it is often used with “もん“ or “もの“ to emphasize what you want to say.
- Meg: It’s been 3 months since I started learning Cantonese. I feel like my Cantonese hasn’t improved very much.
広東語を学び始めて3ヵ月経つけど、全然上達していない気がする。 - Tom: Why?
なんで? - Meg: It’s because I can hear what native speakers say, but I can’t come up with words off the top of my head.
だって、ネイティブが言っている事は聞き取れるんだけど、直ぐに言葉が出てこないんだもの(orもん)。 - Tom: Come on, it’s only 3 months! It’ll take much time to learn to speak the foreign language.
だってさー、たった3ヵ月だもん!外国語を話せるようになるには、もっと時間がかかるよ。
- Ken: The welcome party for new workers is supposed to be held tonight. Do you think you’ll make it to the party?
今夜、新入社員の歓迎会だね。行けそう? - Leo: No, because I have a lot of things to do. I’m going to work overtime.
ううん。だって、やらなきゃいけない事が沢山あるんだもん。残業するわ。 - Ken: Hey, this calls for a celebration! Let’s get some drinks after work.
えっ、お祝いだよ!飲み(に)行こうよ。 - Leo: I suppose, but I have to prepare materials for tomorrow’s meeting. If I have extra time later I’ll drop by.
そうだけど、明日の会議の資料を作らなきゃだもん。時間があったら、行くよ。
- Meg: Are you full? You leave some salad on your plate.
お腹(が)いっぱいなの?サラダが残っているよ。 - Amy: Um, it’s not nice to waste food, but I don't like cucumbers. I feel like I’m a beetle or something when I eat them.
んー、残すのは良くないと思うんだけど、キュウリ(は)嫌いなんだもん(orもの)。食べると、カブトムシになった気分になる。 - Meg: I'm going to eat them instead. Do I look like a beetle, huh?
代わりに食べてあげる。カブトムシに見える? - Amy: No, thanks!
ううん、ありがとう!