sagen
to say
To express something orally or in writing; to pronounce words.
Er hat gesagt, dass er um 17 Uhr kommt.
He said that he is coming at 5 p.m.

to say
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to say
To express something orally or in writing; to pronounce words.
Er hat gesagt, dass er um 17 Uhr kommt.
He said that he is coming at 5 p.m.

'Sagen' (to say/tell) is very often used with a person in the dative (to whom you say something) and a thing in the accusative (what you say). The structure is: subject + sagen + dative object + accusative object.
Kannst du mir bitte die Uhrzeit sagen?
Can you please tell me the time?
'Sagen' (to say) often introduces subordinate clauses, usually with the conjunction 'dass' (that). In such sentences, the conjugated verb comes at the end of the subordinate clause.
Meine Mutter hat gesagt, dass ich mein Zimmer aufräumen soll.
My mother said that I should tidy up my room.
In the meaning of 'anzeigen' (to indicate) or 'bedeuten' (to mean), a thing or a sign can also be the subject of 'sagen' (to say). It describes what information something communicates.
Was sagt die Statistik über die Arbeitslosigkeit?
What does the statistic say about unemployment?
The idiom 'das Sagen haben' (to be in charge / to have the say) is a fixed unit and means 'die Kontrolle oder Autorität haben' (to have control or authority). The noun 'Sagen' is capitalized here.
Zuhause hat meine Mutter das Sagen.
At home, my mother is in charge.
The expression 'sagen wir mal' (let's say) is a typical insertion in spoken language. You use it to make a suggestion or give an estimate.
Das Projekt dauert noch, sagen wir mal, zwei Wochen.
The project will take another, let's say, two weeks.
The expression 'sich (Dativ) nichts sagen lassen' (to not let anyone tell one anything / to ignore advice) describes a stubborn person. Note that the reflexive pronoun is in the dative here because the person would be the recipient of the advice.
Mein kleiner Bruder ist in der Pubertät und lässt sich nichts mehr sagen.
My little brother is going through puberty and doesn't listen to anyone anymore.
to be called / to mean
'sagen' and 'heißen' can both have to do with meaning. 'heißen' is used very often when asking about the meaning of a word, sentence, or sign: 'Was heißt das?' 'sagen' fits better when something conveys a statement, sign, or piece of information: 'Das sagt viel über ihn.' Learners confuse the words because both can sometimes be replaced with 'bedeuten'. As a simple guide: with names and word meanings, 'heißen' is usually more natural. With a message or statement, 'sagen' often fits.

Sein Lächeln sagt mir, dass er zufrieden ist.
His smile tells me that he is satisfied.
Was heißt dieses Wort auf Deutsch?
What does this word mean in German?