There are so many French expressions using the word tenir.
By itself it's a verb that simply means to hold or to take (something).
The conjugaisons are:
je tiens
tu tiens
il, elle, on tient
nous tenons
vous tenez
ils, elles tiennent
Se tenir au courant / Se tenir au jus
One of first expressions I learnt was "Je te tiens au courant" or "Je vous tiens au courant" which means something like "I'll let you know" or "I'll keep you posted." An informal version of this is "Je te tiens au jus."
I specifically remember in one of the French in Action episodes, Mireille says to her friend Hubert when he arrives, "Tiens!" which means something like "Ah...Look what/who we have here!" otherwise it'll just mean "take this" or "hold this"
Je m'y tiens à... = I get cracking and stick to it (the task)
se tenir = to behave, to stay/keep
ne pas tenir compte de = to disregard
tenir à quelquechose = to cherish something
tenir à coeur = to cherish something
tenir bon = to hold one's ground, hold on, keep going
tenir bon contre = stand firm against, stand firm
tenir bon la rampe = hold on (tight), hold out, hang on
tenir compagnie à quelqu'un = to keep someone company
tenir compagnie = to keep company
tenir compte de = to keep in mind, to take into account
tenir debout (figuratively) = to hold water
ne pas tenir à route = not hold water, not make sense
ne pas tenir en place = unable to keep still, have ants in your pants
ne plus tenir en place = have itchy feet
ne pas tenir sur ses jambes = hardly be able to stand
ne tenir qu'à = depend on
ne pas tenir sa parole envers quelqu'un = break a promise, disappoint
ne tenir qu'à un cheveu = hang by a thread
ne tenir qu'à un fil = hang by a thread
ne tenir à rien = not take much
s'en tenir à = stick to, stick with
tenir de bonne source = to have on good authority
tenir de quelqu'un = to take after someone
tenir le bon bout = to be on the right track
tenir le coup = to hold out, to make it through
tenir rigueur à quelqu'un de ne pas = to hold it against someone for not
tenir quelqu'un à l'oeil = to keep an eye on someone
tenir quelqu'un/quelque chose pour = to regard someone/something as
en tenir pour quelqu'un = to fancy/have a crush on someone
il tient que = it depends on
tenez votre gauche/droite = to keep to the left/right
se tenir les côtes = to split one's sides laughing
se le tenir pour dit = take it as read
se tenir à carreau = watch your step
se tenir à l'affût = lie in wait
se tenir à l'affût de = lie in wait for
se tenir à l'écart = shy away
se tenir à la disposition de qqn = be at sb's disposal, be at sb's service
se tenir caché = lie hidden
se tenir debout = stand erect
se tenir derrière = stand behind
se tenir droit = stand (up) straight
se tenir en embuscade = ambush, lurk
se tenir ensemble = stand together
se tenir épaule contre épaule = stand shoulder to shoulder
se tenir épaule contre épaule avec = stand shoulder to shoulder with
se tenir informé = keep yourself informed
se tenir par la main = hold hands
se tenir prêt à = stand to
se tenir prêt à = get ready to
se tenir sur ses gardes = keep yourself on your toes, be on one's guard
tenir à distance = keep from, hold off, shut-away
tenir à jour = keep up-to-date, keep updated
tenir à l'écart = cold-shoulder sb, keep sb away, keep sb out of things
tenir à l'œil = keep tabs
tenir à sa peau = value your life
tenir absolument à faire (une chose particulière) = set on something on doing, set on
tenir chaud = keep warm
tenir compte = consider
tenir compte = take into consideration
tenir compte de = take account of, consider
tenir contre = hold against, hold out against
tenir dans = fit inside, be held in
tenir de = look like, take after, verge on
tenir debout (sens figuré) = make sense, add up
tenir du miracle = verge on the miraculous, be something of a miracle
tenir dur, fort = hang tough
tenir éloigné, à distance = hold-off
tenir en haleine = keep sb in suspense, keep sb on tenterhooks
tenir en laisse = keep on a leash, keep on a lead
tenir en tant que = hold as
tenir ensemble = hold together, holding together
tenir ferme = stand fast, hold steady
tenir fermement = hold tight
tenir informé = keep informed, keep posted
tenir l'alcool = hold your drink
tenir la dragée haute à quelqu'un = hold out on somebody
tenir la forme = keep in good shape, stay fit
tenir la jambe de quelqu'un (familier) = buttonhole somebody
tenir la maison = keep house
tenir la route = stay the course
tenir le fort = hold the fort
tenir le bon bout = be on the right track
tenir le choc = hold on, keep up, face the brunt, cope
tenir le compte de = keep a tally of tally of
tenir le coup = hold on, keep going, keep up, carry on
tenir le crachoir (familier) = hold the floor
tenir le haut du pavé = be on top
tenir le rôle de = play the part of
tenir les bras = pinion
tenir les comptes = keep accounts
tenir lieu de = act as, serve as
tenir lieu de parent = in loco parentis
tenir par = hang by, hold by
Sentence examples
Proverbs/phrases
* Un tiens vaut mieux que deux tu l'auras = A bird in the hand is worth two in the bush
* Il vaut mieux tenir que courir = Better an egg today than a hen tomorrow
* Tenir à quelque chose comme à la prunelle de ses yeux = really care for something, I wouldn't give it away for anything in the world expression I love this book, I wouldn't give it away for anything in the world (or: for all the tea in China).
* S'en tenir aux faits = Stick to the facts
* Qu'à cela ne tienne = That's no problem
(info from here and here)
(image from here)