26
The shape is similar to the worldwide known symbol of multiply: two lines are diagonally across each other. The length of the lines are the same as the frame length. (掛け算の記号×に類似。斜めの線は枠の1辺と同じ長さ)
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( If you don't understand how to read this page, see here first )

the hand-shape-sign:
diagonally wide opened thumb, index and pinkie facing the back hand to the reader, distinguishing it from #25( plus ) sign (手の甲を相手に向け、3本指と腕がX形に)

the hand-movement-sign:

draw the base shape starting from out upper edge, connecting the both lines at the bottom
(外側の上からこの形を書く)

name: sha sound of shake without [i] for the vowel (シェ)

ASCII: X (the similar looking)

phonetic value: unused

definition (single): piled, multiplied situation (also multiply calculation sign) (積まれた状態、算数の積)

verb:

vi. multiply (重なる)
vt. pile (something) (重ねる)

main images in base overlays:

1) Related to piling up/gathering/ group (重ね、集合にかかわって)
2) Mathematical terms as multiple (数学的な用語、積にかかわって)
3) Related to the shape of #26 (字母の形)

Examples of base overlay:

Related to piling up/gathering(重ね、集合にかかわって)

{02(one),26}: together in one; a bunch, a group, become a group (vi. with gd) (束、グループ)
{25(join),26}: gathering, gather (vi. with gd), collect (vt. with ge) (集合)
{26(piled) + lines}: crossed, situation crossed over each other (交差)
{06(opposite),26}: broken down, dissolve (vt. with ge) (ばらばら)
{09(intangible thing),26}: piling happenings/doings (ことがらの積み重ね)
{13 the same,26}: duplication/overlap (v. with gd) (重複)
{13, 26overlap, 31 shape}: symmetry (対称)
{63(gently),26}: accumulation, accumulate (vi. as d-verb, vt. as e-verb) (じわじわ堆積)
{64(very),26}: very quick piling, collect quickly (vt. as e verb) (急な集積)
{26(piled),23}: compound (to change into some other thing) (化合)
{{51,24}( bone),26}:structure (構造)
{46(work),26}: system (しくみ)
{{14,24}rule,26(gathering)}: law (法律)
{26,37(nature)}: chaos (カオス)
{26(group, mass),38}: mass-produced (量産)

{21(heading) or 26 }: collection, collect( vt. with #ge) (収集)
{14(go through),26}: experience (経験)
{15(recognition),26}: deliberation, discretion (分別、慎重)
{28(sheets),26}: any kind of bound thing, bind/stitch( vt. with ge) (綴じたもの、綴じる)
{{28,66}(paper),26}: notebook (帳面)
{{15,30}(information,28,26}: book (本)
{{15,31,28}(picture),26}: picture book (絵本)
{29(material),26}: chemical compound, (chemically) combine (vi. with gd, vt. with ge) (化合物)
{12(friction),26}: interference (干渉)
{12,42(wave),26}: interfere (vi. with gd) (波の干渉)
{{36,42}(sound),26}: composite sound (複合音)
{26,43(closed)}: wringed (絞)
{26,44(open)}: mixture, mix (vi. with gd, vt. with ge) (混合)
{45(relation),26}: net system/network (ネットワーク)
{45,26,28(sheet)}: net (n.) (網)
{47(container),26}: stock, store (vt. with gd) (蓄え)
{48(cover),26}: seal, seal up (vt. with ge) (密封)
{06(opposite),48,26 }: unseal (開封)
{26,50(stuff)}: a heap, a pile (積載品)
{{26,02}(bunch),50}: stacked/bound thing (きちんと束に積まれた品)
{26,58(able): stackable (積み重ね可能)
{35(infinite),26}: sedimentary (永く堆積した)
{26,{35,24,37} rock}: sedimentary rock (堆積岩)
{{10,14}(road),26}: intersection, crossroad (交差点)
{26,{34,65} members} : group, gathering of members (people) (人のグループ)
{65(person),26}: public/people (民衆)
{{10(place),48(cover),67(life)} house,26(group)}: apartment house (集合住宅)
{{66,68},26(gathering)} ( bunch of flowers): (a) bouquet (花束)
{{66,68},{02,27}(group) (a) cluster of flowers (花の房)
{{23,33}(color),26(piled)}: (since mixture color) brown (茶色)

Mathematical terms as multiple (数学的な用語、積にかかわって)

{33,26}: the product (as mathematical meaning) (積)
{{33,32}(number),26}: multiple number (倍数)
{n2,26}: twice/double (2倍)
{n3,26}: three times (3倍)
{n4,26}: four times (4倍)
{n5,26}: five times (5倍)
are used as well.
{{02(one),69(zero)}(ten),26}: ten times (10倍)
{n3,26}{n3,69,26}: three thousand times (3千倍)
{n2,26(multiple)}: even number (偶数)
{27(plural),26}: square (二乗、平方)
{n3,27,26}: cube (3乗)
= n3 {33,36}(times) {33,26}(the product) of two = =
{{27,26},22(origin)}: square root (平方根)

Related to the shape of #26 (字母の形)
{31(shape),26}: the shape of X ( X形)

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