das F
F
The sixth letter of the Latin alphabet.
Das Wort „Fahrrad“ beginnt mit einem F.
The word 'Fahrrad' begins with an F.

F
Loading your saved state.
F
The sixth letter of the Latin alphabet.
Das Wort „Fahrrad“ beginnt mit einem F.
The word 'Fahrrad' begins with an F.

The meaning 'ungenügend' (insufficient/failing) for the grade 'F' is borrowed from the American grading system. In the traditional German school system, grades from 1 (very good) to 6 (insufficient/failing) are given. This meaning is therefore only common in certain, often international contexts.
In Deutschland entspricht die Note 6 einem F.
In Germany, the grade 6 corresponds to an F.
When 'F' is meant as a letter, it is often used in phrases like 'beginnt mit F' (begins with F) or when spelling, for example 'F wie Frankfurt' (F as in Frankfurt).
Mein Name fängt mit F an.
My name starts with F.
The meaning of 'F' is almost always clear from the topic of the conversation. If it is about language, the letter is meant. If it is about music, it is the note. If it is about grades, the school grade is meant.
Diese Melodie enthält ein hohes F.
This melody contains a high F.
F-sharp
'das F' and 'das Fis' both belong to music and refer to notes. The important difference is the pitch: 'das F' is a specific basic note, while 'das Fis' is a semitone higher. On the piano, 'Fis' is the black key directly to the right of 'F'. The words are easy to confuse because they look and sound similar. But to be precise: 'Fis' is not just another word for 'F', but a different note.

Beim Singen trifft Lena das F noch nicht ganz sauber.
When singing, Lena still does not hit the F quite cleanly.
Auf dem Klavier liegt das Fis direkt rechts neben dem F.
On the piano, the F-sharp is directly to the right of the F.