The English language is full of synonyms.  Sometimes the words, mostly nouns, are so close in meaning that they are entirely interchangeable.

A typical dictionary definition of synonyms, such as this one we found in Merriam Webster is:
synonym  (noun)
a word that has the same meaning as another word in the same language
a word, name, or phrase that very strongly suggests a particular idea, quality

noun and verb synonyms

Noun synonyms often mean exactly the same thing:
apothecary – pharmacist
pharmacy – drugstore
drink – beverage
student – pupil
fall (season) – autumn
rubbish – garbage, trash
novice – rookie
dresser – bureau
bush – shrub

Verbs, when they have several same or similar equivalents, can also be synonyms:
melancholy – sad
scream – yell
huge – gigantic
small – tiny
skilled –talented
teach – instruct
droop – sag
abrupt – sudden
absolutely – totally

In other cases however, there is a similar but not a totally
exact fit. Take ‘reticent’ and ‘reluctant’ meanings:
RETICENT : Inclined to keep one’s thoughts, feelings, and personal affairs to oneself. Restrained or reserved in style.
RELUCTANT : Unwilling; disinclined: reluctant to help. Exhibiting or marked by unwillingness: Offering resistance; opposing.
Jane, usually calm and reticent, pleaded passionately for the cause.
John may also be reticent about sharing bad news with you.
Are they reticent? Or are they reluctant? It’s a subtle difference.
The teachers have been reluctant to embrace the new technology.

Some words can seem similar to each other, but there are differences, however subtle:
abhorrent – aberrant
accept – except
adopt – adapt
adverse – averse
affect – effect
afflict – inflict
aggravate – irritate
allude – elude
allusion – illusion

Sometimes there are many words which essentially mean or nearly mean the same thing. For example:
forget.
verb

Synonyms of ‘forget’ include:
not be able to remember
blow
clean forget
consign to oblivion
dismiss from mind
draw a blank
escape one’s memory
fail to remember
let slip from memory
slip up
lose sight of

Create some synonym lists for words that you know. Lists of synonyms are useful when we want to find just the most effective word that conveys our meaning.