The next time you eat a delicious meal, don't call it "yummy." Call it "piquant." It means the same thing, but it sounds way fancier, so you'll appear more intelligent.
Indubitably can be used to replace "certainly" or "definitely." It's something that you can say when you're positive about something, like how the gas prices will indubitably rise again this year.
Ergo simply means "therefore." If you wanted to explain how well you're doing in school, you could say, "I study every single day, ergo, I get great grades."
Alas is "an expression of grief, pity, or concern." That means that you should only use it when something isn't going your way. You can say, "I love The Walking Dead. Alas, I forgot to tape the newest episode."
This word is "used as an intensifier." Don't be confused by that definition, because it's basically just a synonym for indubitably, so you can use it in the same way.
Cherish, of course, means "to hold something dear." So instead of telling your friends that you enjoy spending time with them, tell them that you cherish your evenings together.
Loathe means "to feel intense dislike or disgust for." So the next time you see your arch nemesis, don't claim that you hate them. Say that you loathe them. It has a better ring to it.
Yearning means "to have an intense feeling of longing for something." When you spend a week apart from your boyfriend, tell him that you're yearning to kiss his lips. How romantic!
This word means "to answer (a question or accusation) evasively." It'll be harder to use this one in daily conversations, but you'll find use for it sooner or later.
Becoming means "flattering to a person's appearance." The next time your best friend takes you out to a party, tell her that she's wearing a becoming dress.
Eloquent means "fluent or persuasive in speaking or writing." It's a trait that's incredibly important to have. It'll help you get ahead in your career.
Fancy means "to feel a desire or liking for." Instead of telling your crush that you like him, tell him that you fancy him.
This means "a pleasant, gentle accent." When you love the sound of someone's voice, you can compliment them on their lilt. It'll be a compliment that they've never heard before.
Hence means "for this reason." This is an easy one! It's a synonym for "ergo" and "therefore," so you already know how to use it.
Fetching simply means "attractive." It's just a more unique way of saying it, because the word isn't thrown around all that often.
It's important to expand your vocabulary so that you can come across as intelligent, fancy, or eloquent as you wish.