Radical 讠
4 strokes
認
words 讠 (67c) + person 人 (12) = recognize 认
认为 (122) rènwéi think (that)
[认得 (118) rènde know, understand]

Words have been scrawled up around the school, saying “Harry go home!” — but everyone recognizes the handwriting. / The dwarf teacher finally spots the culprit in action and runs to apprehend him.