Examples:

    look out vs. lookout

look out (for) (verb)

To be careful or vigilant: 

• "Look out for any suspicious activity in the neighbourhood."

lookout (noun)

A person who watches for danger or trouble: 

• "He was stationed as a lookout during the operationA

To watch for danger: 

• "We kept a lookout all night,  but nobody approached."

    cut back vs. cutback

cut back (on) (verb)

To reduce in quantity or number: 

• "We need to cut back on our expenses this month."

cutback (noun)

A decrease in production or services:

•  "The company announced a series of cutbacks due to the economic downturn."

A reduction in quantity:

•  "The budget cutbacks affected many departments."

    make up vs. makeup

make up (verb)

To reconcile after an argument:

•  "Let's make up after our argument; I hate fighting with you."

To invent a story:

•  "He made up an excuse for being late."

makeup (noun)

Cosmetics used to enhance appearance: 

• "She applied her makeup carefully before the important interview."

    run down vs. rundown

run down (verb)

To stop functioning due to lack of energy:

•  "The old clock will run down if you forget to wind it."

To criticize someone or something:

•  "She always runs down her own achievements."

rundown (noun)

A summary or review of information: 

• "Can you give me a quick rundown of what happened at the meeting?"

    check out vs. checkout

check out (verb)

To leave a hotel: 

• "Don't forget to check out of the hotel before noon."

 To investigate or examine something:

•  "You should check out that new restaurant downtown. 

checkout (noun)

The place where you pay for goods in a store; also refers to the process of checking out items from a library, etc.:

•  "There was a long line at the checkout in the supermarket."