General loneliness:
* 寂しい (sabishii): This is the most common and general word for "lonely." It expresses a feeling of emptiness and longing for connection.
* 一人ぼっち (hitoribocchi): This literally means "alone by oneself" and implies a feeling of isolation.
* 孤独 (kodoku): This is a more formal and literary word for "loneliness." It emphasizes a state of being alone and isolated from others.
Other words that can be used depending on the context:
* 切ない (setsunai): This word conveys a feeling of sadness and longing, which can be associated with loneliness.
* 物足りない (monotarinai): This literally means "not enough" and can express a sense of emptiness and dissatisfaction, similar to loneliness.
* 心細い (kokoro bosoi): This conveys a feeling of insecurity and vulnerability, often experienced when one is alone.
The best translation for "lonely" will depend on the specific context and the emotion you want to express.