No, cannot is not a contraction. It is the full one-word negative of the modal can.
Can't is the actual contraction, the short form used in speech: I can't find my keys. In formal writing you will see cannot: Employees cannot enter without a badge.
The report cannot be submitted until all figures are checked. Formal writing leans on the single-word form, so an office memo or a rule keeps cannot intact.
Sorry, I can't make it tonight, something came up. In a text message or spoken reply, the contraction can't is what people naturally say and type.
A nearby mix-up
Spelled with a space, can not is not just another spelling of cannot. Spaced apart, it usually signals a deliberate choice: You can not go and still get your deposit back. The spaced form is rare, and you will mostly see it where the writer wants to stress that not doing something is a real option. If you just want the plain negative meaning, stick with the solid form: She cannot attend on Friday.
If you just want the plain negative meaning, stick with the solid form: She cannot attend on Friday.
A nearby mix-up: can not with a space is not just another spelling of cannot. Spaced apart, it usually signals a deliberate choice: You can not go and still get your deposit back. The spaced form is rare, and you will mostly see it where the writer wants to stress that not doing something is a real option.
If you just want the plain negative meaning, stick with the solid form: She cannot attend on Friday.