Plural of arousal; instances of being aroused, awakened, or stimulated to action or emotion.
From arouse plus -al (suffix creating abstract nouns) with -s marking plural. Each arousal is a discrete event of awakening or stimulation.
Sleep scientists measure 'arousals' when you briefly wake during sleep—even micro-arousals lasting just seconds affect sleep quality, which is why light sleepers feel exhausted despite being in bed eight hours!
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