Say vs tell

Say and tell have similar meanings. They both mean to communicate verbally with someone.

Generally speaking, the verb tell is different because when we use it, we MUST SPECIFY A LISTENER. When we use the verb say we may specify a listener, but we do not have to do so. 

She told ME that she loved Marco.
She said that she loved Marco.
He told EVERYBODY he wanted to stay single.
He said that he wanted to say single.

There is NO double T – No TT – You CANNOT tell to someone.

You may specify the listener when you use SAY, but it is not a requirement.

If you choose to specify a listener with SAY, you must use the preposition “to.”

She said to her classmates that she had wanted to quit many times.

We use “say” very often in dialogues, scripts, and other dramatic formats.

Maria said, “I can’t take it anymore.”
Giovanni said, “You never loved me.”

If you use “tell” in a similar scenario, you must specify the listener. This is not usual for a film script, but it is standard for a novel.

Antonio said to her, “I hope to see you again one day.”

Orders and instructions call for the verb “tell.”

Tell me your name!
Tell the family that I love them!
She told him to sit down.
The doctor told the patient to take the medicine.
The teacher told the student to do the assignment.

EXCEPTIONS
There are a list of expressions with tell where the listener does NOT need to be specified.
Tell the truth
Tell a lie
Tell the time
Tell a story
Tell a secret
Tell a joke
Tell a riddle
Tell a tale
Tell the future

Verbs that follow the say formula – say something (to someone)
admit
agree
announce
claim
complain
confirm
declare
explain
insist
mention
propose
say
suggest

Verbs that follow the tell formula – tell someone something

assure
convince
inform
notify
persuade
reassure
remind
tell

*ASK is the verb we use for questions, NOT say or tell.

Collocations/word pairings with SAY
say hello
say goodbye
say good morning, good afternoon etc.
say something
say nothing
say so
say a prayer
say a few words
say no more
say for sure

Collocations with TELL
tell a lie
tell a story
tell a secret
tell a joke
tell the truth
tell the time
tell the difference
tell the future
tell somebody one’s name
tell somebody the way
tell someone’s fortune

Collocations with ASK
ask a question
ask a favor
ask the price
ask after somebody
ask the time
ask around
ask for something
ask for somebody