मात्रोपज्ञोपक्रमच्छाये नपुंसके

The first member of a तत्-पुरुष समास preserves its original accent when the words 1. मात्रा 2. उपज्ञा 3. उपक्रम and 4. छाया when these words appear as neuter.
Thus भिक्षामात्रं न ददाति याचितः, समुद्र꣡मात्रं न सरोऽपि न सरोऽस्ति किंचन ॥ The word मात्रा is here synonymous with तुल्य, the phrase being भिक्षायास्तुल्यप्रमाणं, and is a Genitive compound. The word भिक्षा is derived from भिक्ष, by the feminine affix अ 3.3.103, and has acute on the final 3.1.3. The word समुद्र has also acute on the final as it is a word denoting 'a sea', (Phit sutra I.2). So also with उपज्ञा, as पाणिनो꣡पज्ञमकालकं व्याकरणम्; व्या꣡डुपपज्ञं दुष्करणम् आपिशल्युपज्ञ गुरुलाघव (see 2.4.21). All these are Genitive compounds. The word पाणिन is derived by अण् affix from पणिन् (पणिनोऽपत्यम् = पाणिन꣡), and has acute on the final, 3.1.3. The word व्याडि being formed by इञ affix has acute on the first 6.1.197, so also आपिशालि ॥ So also with उपक्रम, as आढ्यो꣡पक्रमं प्रासादः, दर्शनी꣡योपक्रमम्, सुकुमारो꣡पक्रमम्, नन्दो꣡पक्रमाणि मानानि ॥ All these are Genitive compounds. The word आढ्य (तत्रैत्यैनं ध्यायन्ति) is derived from आ + ध्यै + क affix added with the force of घञ्, the ध being changed to ढ the word belonging to पृषोदरादि class 6.3.109, and it has acute on the final by 6.2.144. The word दर्शनी꣡य is formed by अनीयर् and has acute on the penultimate नी owing to the indicatory र् 6.1.217. The word सुकुमार has acute on the final by 6.2.172. The word नन्द is formed by अच् 3.1.134. The Tatpurusha compounds ending in उपज्ञा and उपक्रम are neuter by 2.4.21. So also with छाया, as इ꣡षुच्छायम्, ध꣡नुच्छायम् ॥ The word इषु is derived from इष् by उ affix (Unadi I.I3), and it being treated as नित् (Unadi I.9) the acute falls on इ the first syllable 6.1.197. The word धनुस् has also acute on the first by Phit sutra II.3. The compound is a Genitive Tatpurusha -इषूणां छाया; and it is Neuter by 2.4.22. When the compound is not a Neuter we have कुड्यछाया 2.4.25.