I have posted the following in various Threads. After reading a lot of other Threads relating to time, it seems worthwhile to Post it again as a separate Thread. This is approximately what Einstein wrote, which I think is very succinct and pretty much describes it. When an individual ponders his experiences, he can order the events in his life using the criteria of before and after. He can assign a number to each event in such a way that events assigned a lower number occurred before events assigned a higher number. It is convenient to use a device called a clock to provide a consistent set of numbers for use in ordering events. In describing the laws of physics using the language of mathematics, it is convenient (if not necessary) to use a continuous variable called time. This variable similarly orders events based on the criteria of before and after. There is little (if anything) more that can be said relating to time. It is interesting that Albert used bold or italics for before & after, implying that they were undefined terms, not definable via the use of simpler terms or concepts. Note that an axiomatic system requires some undefined primitive terms to avoid various logical problems associated with circular definitions. It is interesting that Albert did not mention the concept of the flow of time from past through the present into the future, which does seem to be a construct (illusion?) of the human mind rather than an objective process associated with reality.