励弧 is read as れいこ (reiko) and means excitation.
れいこ
reiko
はげます
to raise (one's voice)
はげむ
to work hard
はげまし
encouragement
はげみ
れいせいいちばん
giving cries of encouragement at a critical moment
れいきじょうたい
excited state
れいこう
strict observance (of rules, regulations, etc.)
れいしんそし
driven element (antenna)
はげみあい
competition
はげみあう
to vie with another
れいしんかん
exciter tube
れいき
(electrical) excitation