へとへと

へとへと is a mimetic word (オノマトペ) describing extreme physical exhaustion — being completely drained of energy.

GRAMMAR:

Functions as both a na-adjective and adverb.

• Predicate: へとへとだ/です (I'm exhausted)
• Adverbial: へとへとに疲(つか)れる (to get dead tired)

COMMON PATTERNS:

• へとへとになる: to become exhausted
• へとへとに疲(つか)れる: to get dead tired
• へとへとで〜できない: too tired to do ~
• もうへとへとだ: I'm completely wiped out

SIMILAR WORDS:

• くたくた: worn out (similar level, slightly less dramatic)
• ぐったり: limp, collapsed (emphasizes physical collapse)
• ばてる: to be worn out (verb form)
• 疲(つか)れた: tired (general — へとへと is much stronger)

REGISTER:
Casual and conversational. Not used in formal writing.