The mare was up all night and into the morning, mourning her lost foal.
They're both "correct" if the rest of the sentence is written properly, but the "on" form is more common and is less likely to make you sound ultra-pretentious.
My friend is bilingual because he speaks both English and Spanish, fluently.
They are both happy. NOT They is both happy.
Using "back" and "again" together in the same sentence is redundant because both words convey the idea of repetition or return. It is unnecessary to use both in the same sentence because they essentially mean the same thing. Instead, you can choose one word to convey your meaning more clearly and concisely.
Use "that" to introduce essential information that is necessary for the meaning of the sentence. Use "what" to introduce non-essential information that adds extra detail but is not crucial for understanding the sentence.
it is both the morning star & evening star
Celebration because it was over and morning for the loss of life and sexy women.
we both went outside
Both of the tests were easy, to me.
My host was both gracious and hospitable.
It can be both, depending on what tense your using and what kind of sentence you're using it in.
"Vacuoles can be found in both plant and animal cells." is a sentence with that word.
Yes, using words in a sentence helps in learning them. Seeing them in context and using them helps remember both the word and how it is used.
Both sides of the shape were symmetrical.
I am certain that you will find that she is most kind.
Example sentence - It can be difficult to determine if both of the brothers fit the stereotype or not.
With his fingerprints on the murder weapon, the police could draw only one conclusion. The townspeople were left to draw their own conclusions, because both the peddler and the mayor's wife were gone the next morning.