die Rede
speech
An oral presentation or address given in front of a group of people.
Der Präsident hielt eine wichtige Rede an die Nation.
The president gave an important speech to the nation.

speech / talk
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speech
An oral presentation or address given in front of a group of people.
Der Präsident hielt eine wichtige Rede an die Nation.
The president gave an important speech to the nation.

'Die Rede' (speech/talk) is the noun related to the verb 'reden' (to talk/speak). This connection helps you understand the basic meaning.
Wir müssen morgen über dieses Problem reden.
We need to talk about this problem tomorrow.
To express that someone gives an address, German says 'eine Rede halten' (to give a speech). The literal translation with 'geben' is not correct here.
Die Bürgermeisterin wird morgen eine Rede halten.
The mayor will give a speech tomorrow.
The expression 'es kann keine Rede davon sein' (there can be no talk of it) is a fixed formula used to strongly negate something. It is often combined with a 'dass' clause or an infinitive construction with 'zu'.
Es kann keine Rede davon sein, dass wir jetzt aufgeben.
There can be no talk of us giving up now.
In the expression 'jemanden zur Rede stellen' (to confront someone), the person being confronted is always in the accusative.
Der Lehrer stellte den Schüler wegen des Lärms zur Rede.
The teacher confronted the student about the noise.
In the expression 'jemandem in die Rede fallen' (to interrupt someone), the person being interrupted is always in the dative.
Bitte fall mir nicht ständig in die Rede, lass mich aussprechen!
Please don't keep interrupting me; let me finish!
topic / theme
'das Thema' and 'die Rede' are both connected with speaking, but they do not mean the same thing. 'das Thema' is the content that is spoken or written about. 'die Rede' is usually a speech given in front of several people. In the phrase 'von etwas ist die Rede' (there is talk of something), however, 'Rede' means that something is being talked about. This is why learners may confuse the words. For the content, you usually say 'Thema'; for a speech that is given, you say 'Rede'.

In der Besprechung war von neuen Regeln die Rede.
In the meeting, there was talk of new rules.
Zu Hause hat meine Schwester ein wichtiges Thema angesprochen.
At home, my sister brought up an important topic.