Is a decimal number, such as 0.345 a fraction?

Question

Just by semantics alone, would you consider it a fraction when it is not written in a 'fractional' format?

Answer 1

As others have pointed out in the comments, there may be contradictory definitions, and it depends on what the context is.

That being said, have a look at the description of the tag you used for the question:

(fractions): Questions on fractions, i.e. expressions (not values) of the form $\frac ab$, including arithmetic with fractions. Not to be confused with the tag (rational-numbers): fractions denote rational numbers, but the same rational number may be written in different ways as a fraction.

So $0.345$ is definitely a rational number, but in its current form is not a fraction according to this description.