げ, sometimes seen in the kanji form 気（げ） is a suffix in Japanese that expresses that something is ‘giving off the feeling of (A)’, or ‘seems like (A)’. げ is frequently used in relation to emotions, feelings, and things that the speaker generally can’t be 100% sure of due to them not being directly visible.
げ is primarily seen used after the stem form of い-Adjectives, but may also appear following the stem forms of nouns of な-Adjectives. In all of these cases, the addition of げ creates a new な-Adjective meaning ‘(A) seeming’. Due to this, げ may then be followed by either な or に, depending on whether it is altering a verb or a noun later in the sentence.

• 自信（じしん）ありげに見（み）えたかもしれないけど、実（じつ）はめちゃくちゃ緊張（きんちょう）してて吐（は）きそうだった。
  I may have given off the appearance of being confident, but actually, I was super nervous and felt like I was going to throw up.
• 高校生（こうこうせい）たちがファストフード店（てん）で楽（たの）しげに話（はな）しているのを見（み）て、自分（じぶん）が高校生（こうこうせい）の頃（ころ）を思（おも）い出（だ）した。
  When I saw highschool students seemingly having a good time talking to each other at a fast food restaurant, it reminded me of the time when I was a highschooler.
• 高橋（たかはし）くんは不安（ふあん）げに手（て）を上（あ）げました。
  Seemingly nervous, Takahashi-kun raised his hand.

げ is more subjective (based on the speaker’s opinion) than そう, and is considered to be very low confidence. This may be considered a byproduct of the original 気（き）, meaning of ‘attention’, referring to the way that the speaker ‘senses (A)’, regardless of what is actually true for (A) on the inside.