I was thinking mostly of class variables and I'd rather have them be null rather than come up with some default value.

The types in C# and JS are 99% the same; the only differences I know of offhand are "bool" vs "boolean" and "string" vs "String".

Yes, that's the same page I linked to in my answer. ;) Not sure what you mean by "double is the only one available", since you can see on that page that both single (AKA float) and double exist.

I like float. The power to remain accurate at the nano level, while avoiding the overkill at Galactic sizes is indeed a plus. I am probably not as versed as you on the way floating point arithmetic is performed on the various processors with all the bit shifting and swapping tricks and the implicit conversions that are performed at the compile and hardware levels. My statement aims to keep in mind that a float even if considered a Single in some(perhaps most) contexts, it is not the same as a Single. Depending on the requirement of a particular calculation, a float may eat up more instructions cycles than a 'pure' Single/Double, in some cases twice as much. ...and I know, the general consensus on today's machines(above 486) is that float should be faster or at least equal(except for division perhaps), while Single generally outperforms Double but not always. But I still want to keep the difference in mind. At some point, I may run into the last level of optimization that will require to understand precisely how the numeric types are handled at the heart of the system to know what to use where. That of course is mainly required when an operation must be performed constantly(repeatedly) in a fast moving concurrent scenario. ...and you guessed it, I foresee that scenario is/(will be) in my project. Having said that, I admit I am on shifty ground based on mostly educated guessing.

a float even if considered a Single in some(perhaps most) contexts, it is not the same as a Single

float is an alias for System.Single. It's exactly the same.

I dislike using float. I use decimals whenever precision is of paramount importance, and typecast to float only at the very last second if the value absolutely needs to be a float.

Sorry... for my ambiguity. I am stuck in the pre-1990s where 'Single' refers to 'Single Precision FIXED point'...in those days a Single or a Double were fixed point... in today's meaning float implies Single Precision Float usually, double Float -> Double Precision Float. Thus where I used 'Single', I meant Single Precision FIXED point.