TASK DEFINITION: Generate the answer for a given question. The question requires common knowledge of English. Make sure that the answer is in detail, long, consistent with the context, and requires general knowledge of English. To be less repetitive, please vary your language for each question. Give a proper explanation to answer, and if necessary, provide the definition of various terms. And conclude your answer if it's long. If you have used other resources (e.g., Merriam Webster's.) to answer the question, include citations in your answer. You don't need to paraphrase the context of your resources, but make sure that your answer is consistent and complete.
PROBLEM: Invaluable intuitively seems to imply a higher degree of importance. Please explain the difference between valuable and invaluable and in what context you'd use one or the other.

SOLUTION: Technically, invaluable works like priceless. They mean that something is of a value which cannot be expressed in numbers. For example great memories, happiness, health, or whatever else you prefer. They are invaluable, because they cannot be sold or bought. They have no price. On the other hand, valuable means something is of a high value, which can be expressed in numbers. Like a golden ring. It's valuable, because it costs $1000.

PROBLEM: As a programmer I use the word Authentication and the word Authorisation in my code. I'd like to find nice abbreviations or alternative words for each of them that are not ambiguous and has reasonably large 'psychological distance' between. i.e. they don't look too similar i.e 'Auth' is not OK because it is ambiguous. At the moment I have just removed some letters Authtictn Authristn Any suggestions?

SOLUTION: I've worked with IETF people and developers who spend a lot of time on Apache, who tend to use: AuthN - Authentication AuthZ - Authorization You'll find these abbreviations in a lot of IETF technical documents. Yes, I know British spelling prefers s over z (authorisation).

PROBLEM: What is the correct version of this common phrase? First come, first serve First come, first served Gramatically, I believe 2. is the correct form. However, it seems that 1. is commonly employed in spoken and even written English.

SOLUTION:
The second is correct. It is a form of 'Those who come first are served first.'