What are the definitions of float and lag?

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’t process the replies before you send out the mail shot. However, once you have sent them out there will be a delay before you can process them, caused by post and the time taken to fill out the replies. This would be reflected as a lag

Hope this is useful

Regards

Stephen