However, adaptability is more than this. It is also being prepared to adapt each weeks training in the light of the previous week or two, or even specific sessions in your schedule depending on your response to previous sessions. Adapting may be increasing or decreasing the amount of effort you put into a session (not every one should be 100% flat out - that is the route to injury), the number of efforts, the nature of the efforts and/or the recovery periods.
Let me give a couple of examples.
Long runs can be made a much more specific training stimulus for your target race by not running them all at a steady pace. For example it may be helpful to run the first 2/3 of a long run nice and easily, and then pick the pace up for the last 1/3, aiming for target race pace. This can be particularly useful for half and full marathons. You should not do this for all long runs - this would be too much for most people. However the proportion of the long run that you up the pace might vary from 1 mile to 3/4 of the distance. You can also vary the target pace for this faster element. Start with just a short distance at the end and see how you respond. Then adapt your plans week on week depending on how you feel post run and, very importantly, how quickly you recover from your long run.
An alternative example is the emphasis you place on sessions during the week. This is particularly the case with regards to back to back sessions as we do on a Wednesday and Thursday. If you plan to do both, it is best to target one of the sessions and key and adapt the other in some way. How you do this will depend on your current fitness level and your current goals. I saw an excellent example of somebody doing this over the last week. They decided that the 400m session on the Track was what they really wanted to focus on and so they modified the tempo session the night before, making it shorter and slower than they would have otherwise run. This also made sense in that the person had stepped up their long run distance the weekend before. Really good intelligent training.