When a conjunct consonant follows a short vowel is termed guru 'heavy'.,
A hrasva vowel however is not to be called 'light' when it is followed by a conjunct consonant. As the i of शिक्षा 'learning' is a heavy vowel. Thus शिक्षा is derived from शिक्ष + अ 3.3.103, (let the affix अ come after that verb which has a heavy vowel and ends in a consonant when the word to be formed is feminine). So also कुण्डा and भिक्षा.,