This is the 54th most frequent Japanese word.
感
"感" means "feeling," "emotion," or "sensation."
Here, '感' is used in the compound '失望感' (sense of disappointment) to indicate a feeling or emotional state.
彼女の表情から、彼の言葉に対する失望感が伝わってきた。
From her expression, a sense of disappointment toward his words was conveyed.
Here, '感' is part of the word '感覚' (sense or feeling), referring to the impression or sensation experienced.
彼にはユーモアのセンスがあるが、そこから奇妙な感覚も生まれることがある。
He has a sense of humor, but it can also generate a peculiar feeling.
In this sentence, '感' appears in the word '感動的' (moving or emotional) to denote an emotional impact.