筋 （キン） muscle

筋肉 （キンニク） muscle

心筋 （シンキン） heart muscle, cardiac muscle, myocardium

鉄筋 （テッキン） rebar, (iron) reinforcing bar, reinforcing steel, reinforced concrete

筋 （すじ） muscle, tendon, sinew, vein, artery, fiber, fibre, string, line, stripe, streak, reason, logic, plot, storyline, lineage, descent, school (e.g. of scholarship or arts), aptitude, talent, source (of information, etc.), circle, channel, well-informed person (in a transaction), logical move (in go, shogi, etc.), ninth vertical line, seam on a helmet, gristly fish paste (made of muscle, tendons, skin, etc.), social position, status, on (a river, road, etc.), along, counter for long thin things, counter for roads or blocks when giving directions, street (in Osaka), (Edo period) counter for hundreds of mon (obsolete unit of currency)

筋書き （すじがき） synopsis, outline, plot

粗筋 （あらすじ） outline, summary, argument

売れ筋 （うれすじ） popular line (of products), best-selling line, hot sellers