Definition: lit. adventitious, an additional wording generally at the end of roots to show distinctly their form e.g. वदि, एधि, सर्ति etc.; cf. इन्धिभवतिभ्यां च P I.2.6: cf. also भावलक्षणे स्थेण्कृञ्वदिचरिहृतभिजनिभ्यस्तोमुन्, P.III.4.16, सृपिवृदो. कसुन् P. III.4.17 and a number of other sūtras where इ or तिं is added to the root cf. इक्श्तिपौ धातुनिर्देशे, वर्णात्कारः, रादिफः P.III.3.108 Vārt. 2.3. 4, where such appendages to be added to the roots or letters are given. The word अागन्तु is an old word used in the Nirukta, but the term आगन्तुक appears to be used for the first time for such forms by Haradatta; cf. ह्वरोरिति ह्वृ कौटिल्ये, आगन्तुकेकारे गुणेन निर्देशः Padamañjarī on VII.2.31. In the traditional oral explanations the second part of a reduplicated word is termed अागन्तुक which is placed second i. e. after the original by virtue of the convention आगन्तूनामन्ते निवेशः, although in fact, it is said to possess the sense of the root in contrast with the first which is called abhyāsa.A nice distinction can, however be drawn between the four kinds of adventitious wordings found in grammar viz.आगन्तु, इत्, अभ्यास and आगम which can be briefly stated as follows; The former two do not form a regular part of the word and are not found in the actual use of the word; besides, they do not possess any sense, while the latter two are found in actual use and they are possessed of sense. Again the agantu word is simply used for facility of understanding exactly and correctly the previous word which is really wanted; the इत् wording, besides serving this purpose, is of use in causing some grammatical operations. अभ्यास, is the first part of the wording which is wholly repeated and it possesses no sense by itself, while, āgama which is added to the word either at the beginning or at the end or inserted in the middle, forms a part of the word and possesses the sense of the word.