1.  client(n = noun.person) - a person who seeks the advice of a lawyer;
is a kind of case
is a member of attorney-client relation, lawyer-client relation

2.  client(n = noun.person) customer - someone who pays for goods or services;
is a kind of consumer
is a member of business relation
has particulars: buyer, emptor, purchaser, vendee, guest, frequenter, patron, policyholder, shopper, disburser, expender, spender, reader, subscriber, taker, warrantee, john, trick, whoremaster, whoremonger

3.  client(n = noun.artifact) guest, node - (computer science) any computer that is hooked up to a computer network;
is a kind of computer, computing device, computing machine, data processor, electronic computer, information processing system
is a part of computer network

1.  A citizen who put himself under the protection of a man of distinction and influence, who was called his patron. [1913 Webster]

2.  A dependent; one under the protection of another. [1913 Webster]
"I do think they are your friends and clients,
And fearful to disturb you." [1913 Webster]

3.  One who consults a legal adviser, or submits his cause to his management. [1913 Webster]

client, n.
1 a person using the services of a lawyer, architect, social worker, or other professional person.
2 a customer.
3 Rom.Hist. a plebeian under the protection of a patrician.
4 archaic a dependant or hanger-on.

Derivative:
clientship n.

Etymology:
ME f. L cliens -entis f. cluere hear, obey

N  servant, subject, liegeman, servant, retainer, follower, henchman, servitor, domestic, menial, help, lady help, employe, attache, official, retinue, suite, cortege, staff, court, attendant, squire, usher, page, donzel, footboy, train bearer, cup bearer, waiter, lapster, butler, livery servant, lackey, footman, flunky, flunkey, valet, valet de chambre, equerry, groom, jockey, hostler, ostler, tiger, orderly, messenger, cad, gillie, herdsman, swineherd, barkeeper, bartender, bell boy, boots, boy, counterjumper, khansamah, khansaman, khitmutgar, yardman, bailiff, castellan, seneschal, chamberlain, major-domo, groom of the chambers, secretary, under secretary, assistant secretary, clerk, subsidiary, agent, subaltern, underling, understrapper, man, maid, maidservant, handmaid, confidente, lady's maid, abigail, soubrette, amah, biddy, nurse, bonne, ayah, nursemaid, nursery maid, house maid, parlor maid, waiting maid, chamber maid, kitchen maid, scullery maid, femme de chambre, femme fille, camarista, chef de cuisine, cordon bleu, cook, scullion, Cinderella, potwalloper, maid of all work, servant of all work, laundress, bedmaker, journeyman, charwoman, bearer, chokra, gyp (Cambridge), hamal, scout (Oxford), serf, vassal, slave, negro, helot, bondsman, bondswoman, bondslave, ame damnee, odalisque, ryot, adscriptus gleboe, villian, villein, beadsman, bedesman, sizar, pensioner, pensionary, client, dependant, dependent, hanger on, satellite, parasite, led captain, protege, ward, hireling, mercenary, puppet, tool, creature, badge of slavery, bonds, in the train of, in one's pay, in one's employ, at one's call, in bonds.

N  purchase, emption, buying, purchasing, shopping, preemption, refusal, coemption, bribery, slave trade, buyer, purchaser, emptor, vendee, patron, employer, client, customer, clientele, purchased, caveat emptor, the customer is always right.