As a noun:
* He's a bachelor, and he enjoys his freedom. (Refers to an unmarried man)
* The bachelor party was a wild night of celebration. (Refers to a party for a man before his wedding)
* She's a bachelor of science in biology. (Refers to an academic degree)
As an adjective:
* The bachelor apartment was small but cozy. (Refers to a dwelling suitable for a single person)
* The bachelor pad was filled with gadgets and video games. (Refers to a home designed for a single man)
In a phrase:
* He's still a bachelor, but he's looking for love. (Refers to someone who is not married)
* She's a bachelorette, but she's not interested in settling down just yet. (Refers to an unmarried woman)
You can also use "bachelor" in different contexts, depending on the situation:
* "He's a bachelor in the truest sense of the word, he loves his independence."
* "The bachelor party was a raucous affair, with plenty of drinking and dancing."
* "She was awarded a bachelor's degree in English literature."
Ultimately, the best way to use "bachelor" in a sentence depends on the specific meaning you want to convey.