एक-अचो द्वे प्रथमस्य

Upto Sutra 6.1.12 inclusive it is to be understood that for the first syllable two are to be made, i. e. the first syllable is to be reduplicated. This is an adhikara sutra : all the three words viz, एकाचः, and द्वे and प्रथमस्य are to be read in the subsequent sutras upto 6.1.12, before the rule of Samprasarana begins. Thus Sutra 6.1.8 says \when लिट् follows, of an unreduplicated verbal root\. The sense of this sutra is incomplete, unless we supply the three words of this sutra, when it will read thus : \when लिट् follows, there are two in the room of the first portion, containing a single vowel of an unreduplicated verbal root\. Thus from जागृः-जजागार (जागृ + णल् 4.3.82 = जा + जागृ + अ = ज + जागर् + अ 7.4.59 = जजागार \lie awoke\). So also पपाच्, इयाय, आर from the roots पच्, इ and ॠ ॥ The reduplication takes place through the force of the affix that follows. Thus the affixes of the Perfect Tense (लिट्), the Desiderative (सन्), the Intensive (यङ्), the श्लु vikarana, the Aorist in चङ्; all cause reduplication.

The word एकाच means that which consists of one vowel (अच्) ॥ When a stem or root consists of more than one vowel (is a dissyllabic or polysyllabic root), then the एकाच् प्रथमः will be the first syllable: as in जागृ the portion आ is the प्रथम एकाच् 'the first portion consisting of one vowel'. When a root consists of a single vowel, as इ 'to go', then strictly speaking there cannot be any portion which may be called first (प्रथम) or ekach consisting of a single vowel). Here, however, will this rule be applied and इ will be reduplicated, according to the maxim \व्यपदेशिवदेकस्मिन्\ - \An operation which affects something on account of some special designation which for certain reasons attaches to the latter, affects likewise that which stands alone and to which therefore, just because the reasons for it do not exist, that special designation does not attach\. So also in पच् there is no first syllable strictly speaking, but still the rule will apply under the above maxim. In making Reduplications the Rule 1.1.59 should always be borne in mind. Thus पच् + अ (णल् of लिट्) = पाच् पाच् + अ = प पाच् + अ 7.4.59 and 7.4.60 = पपाच ॥

The word द्वि in the sutra indicates that the very word-form is to be doubled or pronounced-twice, and not that another word of similar meaning is substituted. In fact this is not a rule ordaining substitution of two, in the room of one; but of the repetition of the one. Compare 8.1.1.,