“flew” vs. “flu”
Use "flew" as the past tense of "fly"; use "flu" as the short form of "influenza," the illness.
flew
"Flew" is the simple past tense of the verb "fly," describing movement through the air at some point in the past ("the plane flew over the mountains"). It follows an irregular Old English verb pattern, part of the same ancient strong-verb family as "fly/flew/flown," tracing back to Old English "fleogan."
flu
"Flu" is the informal short form of "influenza," the contagious viral respiratory illness that causes fever, aches, and fatigue. "Influenza" itself comes from Italian, originally referring to the astrological "influence" believed in earlier centuries to cause outbreaks of disease; the shortened form "flu" became common in English usage by the late 19th century, especially after the major flu epidemics of that era made the shorter word convenient for everyday use.
The real distinction
These two share nothing beyond an accident of pronunciation — "flew" is a verb form describing past flight, and "flu" is a noun naming an illness — so the only real risk is a spelling slip in fast writing, since context makes the intended word obvious almost immediately in any real sentence. Nobody would confuse the meanings themselves; the error is purely typographical, most likely to occur when someone is typing quickly and the fingers default to the more frequently typed of the two spellings. A fast check: if the sentence describes something moving through the air in the past tense, it's "flew"; if it describes being sick with a seasonal illness, it's "flu." Because "flu" is a clipped form of a much longer word, it's worth remembering it never takes the "-ew" ending that marks the past tense of "fly" — "flu" is simply a fixed, unchanging noun, with no verb behavior at all. Health writing and news coverage of seasonal outbreaks rely on "flu" heavily as shorthand, while "flew" shows up constantly in narrative and travel writing describing motion, so the surrounding subject matter alone almost always settles which spelling a sentence needs before grammar even enters into it. It also helps that "flu" almost never appears without an article or a possessive nearby ("the flu," "her flu," "a bad flu"), functioning exactly like any ordinary illness noun, while "flew" sits directly after a subject as the sentence's main verb, with no article possible in front of it at all. It's also worth remembering that "the flu" in everyday speech is often used loosely to describe several different viral illnesses with overlapping symptoms, while true influenza is a specific, seasonally tracked virus that public health agencies monitor and name by strain each year. That's part of why phrases like "stomach flu" are technically misnomers in medical terms, even though they're near-universal in casual speech, since that illness is usually unrelated to the influenza virus at all.
Examples with “flew”
- The geese flew south as the weather turned cold.
- She flew to Chicago for the conference last week.
- The kite flew higher than anyone expected.
- He flew across the finish line in record time.
- The plane flew through turbulence for nearly an hour.
- A flock of starlings flew overhead at dusk.
- The ball flew over the fence for a home run.
- They flew home just before the storm hit.
Examples with “flu”
- Half the office came down with the flu last week.
- She got her flu shot early this year.
- The flu season peaked earlier than usual this winter.
- He missed three days of work with the flu.
- Doctors recommend the flu vaccine for older adults especially.
- The flu left her exhausted for nearly two weeks.
- A bad strain of flu spread quickly through the school.
- Stomach flu is technically unrelated to the influenza virus.
Memory trick
"Flew" has the same "ew" ending as "grew" and "knew" — all irregular past-tense verbs. "Flu" is a short, clipped noun, missing letters the way the illness leaves you missing energy — think of it as "influenza" with most of the word cut away.