Englishfor English speakers
f
Noun
—
F is the sixth letter of the alphabet.
"e" comes before "f"
—
In some schools, an F is a grade that shows that you have failed completely.
This student has not made any attempt in the exam; he only got an F.
toxin
—
noun
a poisonous substance produced during the metabolism and growth of certain microorganisms and some higher plant and animal species