To show or display something so that someone can see it.
子どもに新しいおもちゃを見せると、大きな声で喜んだ。
I showed the new toy to the child, and they shouted with joy.
写真を見せてください。友達に見せたいんです。
Please show me the photos. I want to show them to my friends.
店員が商品のサンプルをカウンターに並べて見せた。
The clerk lined up the product samples on the counter and showed them.
To make something or someone appear a certain way; to present an appearance of ...
彼は若く見せるために髪型を変えた。
He changed his hairstyle to look younger.
その店は安く見せるためにセールを強調している。
The shop emphasizes sales to make things look cheap.
彼女は疲れているのを見せまいと笑って見せた。
She smiled to hide how tired she was.
To make something worth watching; to perform in a way that entertains or impresses an audience (often written 観せる).
あのダンサーは舞台で客を魅了する演技を観せた。
That dancer put on a captivating performance on stage.
監督は試合の最後に観客を観せるための大技を準備していた。
The director had prepared a big move at the end of the game to wow the audience.
マジシャンは手品で子どもたちに不思議を観せた。
The magician showed wonders to the children with his tricks.
To have something (e.g., an antique) examined or appraised by a specialist.
祖父の古い時計を店に見せて、鑑定してもらった。
I took my grandfather's old watch to the shop to have it appraised.
この絵は本物かどうか専門家に見せる必要がある。
We need to have an expert look at this painting to see if it's genuine.
To have an injury or illness examined by a doctor; to take someone to see a doctor (also written 診せる).
熱が続くので、母は子どもを病院に見せに行った。
Since the fever continued, my mother took the child to the hospital to be seen.
頭をぶつけたので、念のために医者に診せてください（診せる）。
You hit your head, so for safety's sake please have a doctor examine it (診せる).
Auxiliary: attached to the -te form of a verb to indicate making a conspicuous show of doing something; performing an action conspicuously or theatrically.
彼女は悲しそうに泣いて見せたが、本当は平気だった。
She pretended to cry sadly, but in truth she was fine.
子どもは新しいおもちゃを友だちに見せびらかして見せた。
The child showed off the new toy to his friends.
Auxiliary: attached to the -te form of a verb to express determination to do something at any cost or to show others one will accomplish it (e.g., 'I'll do it and show you').
任せて、必ず成功させてみせる。
Leave it to me — I'll make it succeed, you'll see.
苦労してでも目標を達成してみせると彼は言った。
He said he would achieve the goal even if it meant hardship — he'd show them.