When you make a solution of anything, you are dissociating the ions or molecules of the substance you are dissolving into the individual molecules of water. So it depends on which end of the spectrum you are looking at. If you start with the sodium hydroxide, say 12 molar strength as a solid, and dissolve that in water, it will weaken, or dilute, the strength of the sodium hydroxide. If you are talking about the water, which has no sodium hydroxide before you add it, you will strengthen the solution, increading the number of sodium and hydroxide ions available within the solution. Water, pure, distilled water, has a pH of about 7 on the pH scale. When you add sodium hydroxide, the pH swings to the higher end of the scale, as high as a 12 or 13, which indicates the presence of a strong base. Think about it in terms of adding sugar to water, which would make a sweet drink. If you want more sweetness, add more sugar; if you want less sweetness, add less sugar.
Now water is neutral compound as we all know. and Sodium hydroxide is an alkaline or base.
If NaOH is added to water, then the solution will become basic in nature. Now the strength of a basic solution is given by its pOH value (it is opposite to pH)
pOH = -log [OH]
So the strength of the solution is directly proportional to the amount of NaOH added.
if more NaOH is added it will become more basic.
[Note: less the pOH greatre will be the basic strength. it sis like pH but they are opposite, if pH is high then the soltuion is less basic and vise versa.
there is a relation, pH + pOH = 14, pOH= 14-pH, so we can see that if pH is increased the pOh value decreases whcih indicates that the solution is more basic]
hope ity has help you