How many strings are on a double bass?

The terms double bass, contrabass, and simply bass all refer to this one instrument. It is 6 feet tall and has four thick strings tuned to sound EE AA D G (EE = third E below middle C; G = second G below middle C) and notated an octave higher. A low fifth string is sometimes added, tuned to the C below the E string. The bass is tuned in 4ths instead of the 5ths used by all the other string instruments.

https://www.britannica.com/art/double-bass