Bhashya
शिक्षा शिक्ष्यते अनयेति वर्णाच्चारणलक्षणम्, शिक्ष्य-न्ते अस्मिन् इति वा शिक्षा वर्णादय ।शिक्षैव शीक्षा ।दैर्घ्य छा दसम ।ता शीक्षा व्याख्यास्याम विस्पष्टम् आ स-मन्तात्प्रकथयिष्याम ।चक्षिङ ख्याञादिष्टस्य व्याङ्पूर्वस्यव्यक्तवाकर्मण एतद्रूपम् ।तत्र वर्ण अकारादि ।स्वर उदा-त्तादि ।मात्रा ह्रस्वाद्या ।बल प्रयत्नविशेष ।साम वर्णा-ना मध्यमवृत्त्योच्चारण समता ।सन्तान संतति , संहितेत्य-र्थ ।एव शिक्षितव्योऽर्थ शिक्षा यस्मिन्नध्याये, सोऽयशीक्षाध्याय इति एवम उक्त उदित ।उक्त इत्युपस-हारार्थ ॥
In plain words
Phonetics is that discipline through which instruction is imparted, defined by the rules governing the pronunciation of sounds. Alternatively, it is called Śikṣā because within it letters and other elements are taught. The same word appears as Śīkṣā through vowel lengthening in Vedic usage. We shall now explain this Śīkṣā with absolute clarity, setting it forth from every angle. This term derives from the verbal roots for speaking and declaring when prefixed by vi and ā, signifying clear expression. Herein, 'letter' refers to sounds beginning with 'a'; 'tone' refers to pitches such as high tone; 'measure' refers to durations such as short vowels; 'effort' denotes specific articulatory exertion; 'sameness' is the evenness of sounding letters at a moderate tempo; and 'continuity', 'extension', and 'junction' all signify euphonic combination. Thus, because the subject matter to be studied—Śikṣā—resides in this section, it is designated as the Śīkṣādhyāya. Thus it has been fully set forth and explained, with the final reiteration serving to conclude the teaching.
Close to the Sanskrit
Shiksha is that by which instruction is given; it is characterized by the pronunciation of letters. Or, 'Shiksha' is that wherein letters and other elements are taught. Shiksha itself is also written as Shīkṣā, with lengthening in Vedic usage. Then we shall explain this Shīkṣā very clearly, setting it forth comprehensively. This is the derived form from the verbal roots cakṣiṅ and khyāñ when preceded by the prepositions vi and āṅ, conveying the action of clear speech. Among these, 'letter' means 'a' and others; 'tone' means high pitch and others; 'measure' means short duration and others; 'effort' means specific articulatory exertion; 'sameness' means evenness in pronouncing letters at a medium tempo; 'continuity', 'extension', and 'junction' mean close euphonic combination (samhitā). Thus, the subject matter to be learned—Shiksha—is contained in this chapter; therefore this is the Śīkṣādhyāya. Thus it has been stated and expressed. The word 'uktaḥ' is for the purpose of concluding.