A double helix is often referred to as a "twisted ladder." It consists of two spirals bound together.
It's the shape of the DNA molecule, a pair of parallel helices intertwined about a common axis.
A double helix is two helixes.
The coiled structure of double-stranded DNA in which strands linked by hydrogen bonds form a spiral configuration, with the two strands oriented in opposite directions.
Francis Crick and James Watson