1.  approximation(n = noun.cognition) estimate, estimation, idea - an approximate calculation of quantity or degree or worth; "an estimate of what it would cost"; "a rough idea how long it would take"
is a kind of calculation, computation, figuring, reckoning
has particulars: scalage, credit, credit rating, dead reckoning, guess, guessing, guesswork, shot, guesstimate, guestimate, overestimate, overestimation, overrating, overreckoning, underestimate, underestimation, underrating, underreckoning

2.  approximation(n = noun.attribute) - the quality of coming near to identity (especially close in quantity);
is a kind of similarity

3.  approximation(n = noun.communication) - an imprecise or incomplete account; "newspapers gave only an approximation of the actual events"
is a kind of version

4.  approximation(n = noun.act) bringing close together - the act of bringing near or bringing together especially the cut edges of tissue;
is a kind of connection, connexion, joining

1.  The act of approximating; a drawing, advancing or being near; approach; also, the result of approximating. [1913 Webster]
"The largest capacity and the most noble dispositions are but an approximation to the proper standard and true symmetry of human nature." [1913 Webster]

2.  An approach to a correct estimate, calculation, or conception, or to a given quantity, quality, etc. [1913 Webster]

3.  A continual approach or coming nearer to a result; as, to solve an equation by approximation. [1913 Webster]

N  relation, bearing, reference, connection, concern, cognation, correlation, analogy, similarity, affinity, homology, alliance, homogeneity, association, approximation, filiation, interest, relevancy, dependency, relationship, relative position, comparison, ratio, proportion, link, tie, bond of union, relative, correlative, cognate, relating to, relative to, in relation with, referable or referrible to, belonging to, appurtenant to, in common with, related, connected, implicated, associated, affiliated, allied to, en rapport, in touch with, approximative, approximating, proportional, proportionate, proportionable, allusive, comparable, in the same category, like, relevant, applicable, equiparant, relatively, pertinently, thereof, as to, as for, as respects, as regards, about, concerning, anent, relating to, as relates to, with relation, with reference to, with respect to, with regard to, in respect of, while speaking of, a propos of, in connection with, by the way, by the by, whereas, for as much as, in as much as, in point of, as far as, on the part of, on the score of, quoad hoc, pro re nata, under the head of, of, in the matter of, in re, thereby hangs a tale.

N  similarity, resemblance, likeness, similitude, semblance, affinity, approximation, parallelism, agreement, analogy, analogicalness, correspondence, homoiousia, parity, connaturalness, connaturality, brotherhood, family likeness, alliteration, rhyme, pun, repetition, sameness, uniformity, isogamy, analogue, the like, match, pendant, fellow companion, pair, mate, twin, double, counterpart, brother, sister, one's second self, alter ego, chip of the old block, par nobile fratrum, Arcades ambo, birds of a feather, et hoc genus omne, gens de meme famille, parallel, simile, type, image, photograph, close resemblance, striking resemblance, speaking resemblance, faithful likeness, faithful resemblance, similar, resembling, like, alike, twin, analogous, analogical, parallel, of a piece, such as, so, homoiousian, connatural, congener, allied to, akin to, approximate, much the same, near, close, something like, sort of, in the ballpark, such like, a show of, mock, pseudo, simulating, representing, exact, lifelike, faithful, true to nature, true to life, the very image, the very picture of, for all the world like, comme deux gouttes d'eau, as like as two peas in a pod, as like as it can stare, instar omnium, cast in the same mold, ridiculously like, as if, so to speak, as it were, as if it were, quasi, just as, veluti in speculum, et sic de similibus, tel maitre tel valet, tel pere tel fils, like master, like servant, like father, like son, the fruit doesn't fall far from the tree, a chip off the old block.

N  numeration, numbering, pagination, tale, recension, enumeration, summation, reckoning, computation, supputation, calculation, calculus, algorithm, algorism, rhabdology, dactylonomy, measurement, statistics, arithmetic, analysis, algebra, geometry, analytical geometry, fluxions, differential calculus, integral calculus, infinitesimal calculus, calculus of differences, dead reckoning, muster, poll, census, capitation, roll call, recapitulation, account, notation, addition, subtraction, multiplication, division, rule of three, practice, equations, extraction of roots, reduction, involution, evolution, estimation, approximation, interpolation, differentiation, integration, abacus, logometer, slide rule, slipstick, tallies, Napier's bones, calculating machine, difference engine, suan- pan, adding machine, cash register, electronic calculator, calculator, computer, arithmetician, calculator, abacist, algebraist, mathematician, statistician, geometer, programmer, accountant, auditor, numeral, numerical, arithmetical, analytic, algebraic, statistical, numerable, computable, calculable, commensurable, commensurate, incommensurable, incommensurate, innumerable, unfathomable, infinite, quantitatively, arithmetically, measurably, in numbers.

N  approach, approximation, appropinquation, access, appulse, afflux, affluxion, advent, pursuit, approaching, approximative, affluent, impending, imminent, on the road, Int, come hither!, approach!, here!, come!, come near!, forward!.