As with other homophones, the words threw, through, and thru may sound alike but have different meanings and uses. Threw and through have very distinct meanings while thru is generally used only in informal writing.
The term threw is the simple past tense of the verb throw meaning “to propel something with force through the air by a movement of the arm and hand.”
“Young woman, 26, ‘threw boiling water over her boyfriend’s pal during a Valentine’s Day bust-up’”
“Prosecutors won’t charge police officer who threw black high school student out of her chair onto the ground for refusing to give up her cellphone”
“‘Grinning sex attacker’ threw table at woman, grabbed her throat and pinned her down to sexually assault her”
It may also mean “to cause to enter suddenly a particular state or condition.”
“Corruption threw country into abyss of terrorism: Siraj”
The News International
“Trevor Noah: How Trump threw Republicans in Congress ‘under the bus'”
“Miley Cyrus and Liam Hemsworth Reportedly Threw a Secret New Year’s Eve Wedding”
On the other hand, through is mostly used as a preposition or adverb to denote “moving in one side and out of the other side of an opening, channel, or location.”
“A Gathering of the Global Elite, Through a Woman’s Eyes”
New York Times
“The Photos We Loved: President Obama Through Pete Souza’s Lens”
“Thousands fill Loop after Women’s March rally in Chicago draws estimated 250,000”
It may also mean “continuing in time toward completion of a process or period.”
“Pod save America: 12 podcasts to get you through the Trump presidency”
“Growing Up Obama: Malia and Sasha Through the Years”
“Study suggests surprising reason killer whales go through menopause”
Meanwhile, the term thru is simply an informal spelling of the word through and is usually not recommended to be used in formal writing as it is considered less serious than its original counterpart.
“Website Thru The Nite: The Countdown Has Begun”
“Cold Rain Thru Wednesday. Little Icing North And West”
WPRI 12 Eyewitness News
“Heavy Wet Snow and Ice Expected Monday Night Thru Tuesday”
The Vermont Standard
Another term that may add up to the confusion would be the adjective thorough which means “complete with regard to every detail” or “performed or written with great care and completeness.” This is attributed to its almost identical spelling with through.
“Senate should take its time, be thorough in vetting Trump nominees”
The Seattle Times
“Acting president calls for thorough readiness against potential N. Korea provocations”
“Senator Chuck Schumer Calls for a ‘Thorough’ Vetting of Trump’s Nominees”
Hopefully, you will never go through the confusion with using these words that threw you off of your writing game. Just remember to establish what message you want to convey in your sentence to help you choose the right term.