MS Project

Hi Mark

Thank you for your question

Float is the amount of time that the finish date of a task can be delayed before it delays either its successor tasks or the completion of the project. Free Float refers to the former and total float to the later. Obviously tasks on the critical path will have zero Float.

Note project uses the term slack to mean float, as this is the American term for it.

Lag is a specific delay built into a task dependency. For example, if you are sending out a mail shot and then processing the replies, you would link the two tasks as obviously you can