अपिः पदार्थसम्भावनान्ववसर्गगर्हासमुच्चयेषु

The word अपि is कर्म-प्रवचनीय when it implies, the sense of word 'understood' ('somewhat') or 'possibility' (e.g. 'even' in the sense of such a great person), or permission to do as one likes, ('if you like'), or censure ('even' in the sense of what is disgraceful); or collection ('and').
The word पदार्थ means the sense of another word which is not expressed but has to be supplied. As सर्पिषोऽपि स्यात् there may be perhaps a drop of ghee मधुनोऽपि स्यात्. Here some word like vindu 'a drop,' stoka 'a little' matra, 'a measure' &c., has to be understood. The word संभावन means possibility, a supposition. As, अपि सिंचेत् मूलकसहस्रं क्षणेनैकेन possibly may sprinkle a thousand trees in one moment; अपि स्तुयाद् राजानं he may praise possibly, a king. In the above cases it is used with the potential mood. अन्वसर्ग means indifference on the part of the speaker where he permits another to do as he likes. It is used with the Imperative mood. As अपि सिंच you may sprinkle if you like. अपि स्तुहि you may praise if you like. The word गर्हा means censure, contempt or reproof. As धिक्जाल्मं देवदत्तमपि सिंचेत् पलाण्डुम्. The word समुच्चय means cumulative. As अपि स्तुहि—अपि सिंच praise as well as sprinkle.
In all the above instances, the word not being an upasarga, does not change the स into ष.