Step 1: Sort the types of capital
A company has four common levels of share capital. Nominal capital is the biggest. Then comes issued capital, then subscribed capital, and the smallest is paid up capital, which is what has been actually collected.
Step 2: Match the descriptions
Option 1 is issued capital. Option 2 is subscribed capital. Option 4 is paid up capital. Option 3 is the limit set in the Memorandum, which is nominal capital.
Step 3: Answer
Nominal capital, authorised capital and registered capital all mean the maximum amount the company may issue, so option 3 is correct.
Final Answer:
Option 3 defines nominal share capital.
\[ \boxed{\text{Option 3}} \]