独(ひと)り言(ごと)soliloquy, monologue, speaking to oneself

彼(かれ)は一人(ひとり)で独(ひと)り言(ごと)を呟(つぶや)いている。

He is muttering to himself alone. {soliloquy, monologue, speaking to oneself}

同僚(どうりょう)は「しまった」と小声(こごえ)で独(ひと)り言(ごと)を言(い)いました。

My colleague muttered 'damn it' under his breath. {soliloquy, monologue, speaking to oneself}

隣(となり)の席(せき)の人(ひと)がブツブツと独(ひと)り言(ごと)を呟(つぶや)いていたので席(せき)を移動(いどう)した。

I changed seats because the person next to me was mumbling to himself. {soliloquy, monologue, speaking to oneself}

今(いま)は静(しず)かにするべきなので、息子(むすこ)の独(ひと)り言(ごと)を止(と)めねばならない。

Since it's time to be quiet now, I have to stop my son's soliloquy. {soliloquy, monologue, speaking to oneself}

独(ひと)り言(ごと)は不気味(ぶきみ)がられると分(わ)かりつつも、癖(くせ)なのでやめる事(こと)が出来(でき)ません。

While I understand that talking to myself can be perceived as creepy, I can't stop because it's a habit. {soliloquy, monologue, speaking to oneself}