Lose is a verb in the base form meaning to not keep something, not win, or to no longer have something. Lost is the past form of lose and is used for completed past events. Lost is also an adjective meaning not found, confused, or not knowing where you are. The key is to decide whether you need a present or infinitive verb form lose, a past verb form lost, or an adjective lost.

Lose describes an action: something happens and you fail to keep it, you cannot find it, or you do not win. It can refer to objects, games, opportunities, time, or qualities like patience and control. Lose focuses on the action of no longer having or not succeeding. It often needs an object after it, like lose your keys or lose the match.

Lost is the simple past and past participle of lose. Use lost for actions completed in the past, often with a past time reference like yesterday, last week, or earlier. Use have lost for present perfect when the loss happened before now and matters now. Use had lost for past perfect when one past loss happened before another past event.

Subject	Form	Example
I	lose lost have lost	I lose my temper sometimes, but I lost it yesterday and I have lost it before.
you	lose lost have lost	You lose focus easily, you lost focus in class, and you have lost focus lately.
he	loses lost has lost	He loses his keys often, he lost them yesterday, and he has lost them again.
she	loses lost has lost	She loses track of time, she lost track last night, and she has lost track recently.
it	loses lost has lost	It loses battery fast, it lost power earlier, and it has lost power before.
we	lose lost have lost	We lose games sometimes, we lost last weekend, and we have lost a few lately.
they	lose lost have lost	They lose confidence quickly, they lost confidence after the mistake, and they have lost confidence this year.

Lost can be an adjective, not a verb. As an adjective, it describes something that cannot be found, or a person who is confused or without direction. In this use, it often appears after be, seem, feel, look, or get. If you can replace it with confused or missing, lost is likely an adjective.

Use lose for habits, repeated actions, general truths, and future meaning with will or going to. Use lost for a completed past event, especially when you mention when it happened. Use have lost when the result is important now, such as something still missing. Choosing the right time meaning prevents mixing lose with past time words like yesterday.

Rule	Example
Use lose for present or future meaning	I lose my keys sometimes. I will lose my mind if it happens again.
Use lost for a finished past event	I lost my keys yesterday.
Use have lost when it is still true now	I have lost my keys, so I cannot get in.
Avoid lose with clear past time words	Correct: I lost my wallet last night.

Lose appears in several common verb patterns that help you recognize it quickly. Lose is often followed by a noun, like lose money, or a noun phrase, like lose your way. It is also common in fixed expressions like lose weight, lose interest, and lose track of time. These patterns always use lose in the base form and lost in the past.

Word/Phrase	Definition	Example
lose weight	become lighter	She wants to lose weight this year.
lose interest	stop being interested	I lost interest halfway through the movie.
lose your way	become confused about direction	We lost our way in the old town.
lose track of time	stop noticing time passing	I lose track of time when I read.
lose control	fail to control something	He lost control of the car on the ice.

When talking about competitions, lose means you do not win. It can take an object like lose the match, or it can be used without an object in context like We lost. The past form lost is extremely common in sports and games, and it can be paired with by to show the margin. This meaning is different from misplacing objects but uses the same verb forms.

Rule	Example
Use lose to mean not win	We always lose against them.
Use lost for past results	We lost the match on Saturday.
Use lose to someone for the opponent	They lost to a stronger team.
Use lose by for the margin	She lost by two points.

Lost can also be a noun in specific contexts, especially in set phrases and signs. The most common is lost and found, which refers to a place or system for items that were found after being lost. You may also see the plural losses for negative results such as financial losses or team losses. This noun use is separate from the verb lose.

Lose and lost are easy to confuse in writing because they share the same root but look different. Lose ends with -se and has a long vowel sound. Lost ends with -st and marks the past form, and its vowel is shorter. Keeping the spelling connected to time meaning helps you choose the correct word.

Rule	Description	Notation	Example
Lose vowel	Long oo sound	/luːz/	I might lose my phone.
Lost vowel	Short o sound in many accents	/lɔst/ or /lɑst/	I lost my phone yesterday.
Final consonants	Lose ends with z sound, lost ends with st	/z/ vs /st/	lose vs lost

To choose correctly, ask what role the word plays in your sentence. If it is the main action and the time is now, general, or future, use lose. If the action happened in the past, use lost. If the word describes a person or thing as missing or confused after be or feel, use lost as an adjective.