Change
Transformation
Change and change equals even more change.
へんか
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
コウイチは、天こうの変化にとてもびん感で、雨の日はよくへん頭痛をわずらっています。
Koichi is very sensitive about changes in the weather and he often gets migraines on rainy days.
十年前におとずれた時とくらべて、東京はずいぶんと変化しましたね。
Tokyo has changed a lot since I visited ten years ago.
うわ！すごいね。既に変化が現れているのが分かるよ。
Wow! This is amazing! I can see the change already.