Sale vs Sale 

Sale is an adjective - dirty. Saler means to salt.
Sale is the noun for vente or solde.

Scène vs Scene 

Scène refers to the stage as well as all senses of scene.
Scene means scène or décor.

Secret vs Secret

Secret is a semi-false cognate; in addition to the English sense of secret, the French word can mean reserved or reticent: Il est secret - He is reserved.
Secret refers to something that is not public knowledge.

Sécurité vs Security 

Sécurité means safety as well as security.
Security can refer to une caution or guarantie in addition to la sécurité.

Seize vs Seize

Seize is the number sixteen.
Seize is the verb saisir.

Sensible vs Sensible

Sensible means sensitive or even nervous, as in pas recommandé aux sensibles - not recommended for people of a nervous disposition. 
Sensible means to show good sense, e.g., in making decisions: sensé, raisonnable, sage.

Simple vs Simple

Simple is a semi-false cognate. It can mean plain, one-way (as in a street or a plane ticket), or singles (as in tennis).
Simple is equivalent to its French cognate.

Situation vs Situation 

Situation is a semi-false cognate. In addition to situation, it can refer to location or position.
Situation refers to situation or conjoncture.

Social vs Social

Social is a semi-false cognate. In addition to the English sense, it often refers to the world of industrial or labor relations: partenaires sociaux  - management and labor.
Social describes someone/something that enjoys the company of others: a social creature - une créature sociale.

Son vs Son

Son is the third person singular possessive adjective as well as the French noun for sound.
Son is the English word for fils.

Sortir vs Sort 

Sortir means to go out or to leave.
Sort as a verb means classer, trier, or séparer, while the noun means genre or espèce.

Source vs Source 

Source is a semi-false cognate. In addition to source, it can refer to a spring (source of water).
Source is une source or une origine.

Souvenir vs Souvenir

Souvenir is a semi-false cognate. In addition to the English sense, it is the French verb "to remember" as well as a noun for memory, recollection, and remembrance.
Souvenir is a keepsake or memento.

Spécial vs Special

Spécial is a semi-false cognate. In addition to special, it can mean strange: Elle est très spéciale - She is very peculiar.
Special refers to something out of the ordinary: a special event - un événement spécial.

Spectacle vs Spectacle

Spectacle refers to any sort of exhibition: un spectacle de danse - a dance performance or to something that others can watch: le spectacle de la rue - the bustle on the street.
Spectacle is a semi-false cognate. It can mean an exhibition, but is usually used with a negative connotation: you made a spectacle of yourself - tu t'es donné en spectacle. Spectacles is the British English word for lunettes.

Sportif vs Sportive

Sportif refers to something related to sports: un journal sportif - a sports magazine or someone who is fond of sports: un homme sportif - an athletic man.
Sportive means playful or merry - folâtre, badin.

Stable vs Stable

Stable means stable, steady, or unmoving.
Stable is a semi-false cognate. In addition to meaning the adjective stable, it can be the noun écurie.

Stage vs Stage

Stage is an internship or training period.
Stage is une scène, le théâtre, un estrade, or une étape.

Store vs Store

Store refers to a blind, shade, or awning.
Store is any sort of magasin or provision as well as the verb mettre en réserve or conserver.

Suit vs Suit 

Suit is from the verb suivre - to follow.
Suit can be a noun - costume, tailleur, tenue, etc. or a verb - convenir à.

Supplier vs Supplier

Supplier is the verb to beseech or implore.
Supplier is a noun for one who supplies - fournisseur.

Supporter vs Support

Supporter means to support or hold up, as well as to endure or put up with something.
Support means all of these things, but in the sense of enduring something, soutenir is the more common translation.

Thé vs The 

Thé means tea.
The is the definite article le, la, or les.

Tirer vs Tire

Tirer means to pull.
Tire as a verb means fatiguer or lasser, as a noun it means un pneu.

Trépasser vs Trespass

Trépasser means to pass away.
Trespass means to invade another's property: s'introduire sans permission.

Truc vs Truck

Truc refers to an unnamed or unknown object: thing, trick, thingamajig.
Truck is a heavy motor vehicle for carrying things: un camion.

Truculent vs Truculent

Truculent means vivid, colorful, racy, larger than life, etc.
Truculent describes someone who is aggressive or predisposed to fight: brutal, aggressif.

Ultérieur vs Ulterior

Ultérieur means later or subsequent: la séance est reportée à une date ultérieure - the meeting is postponed to a later date.
Ulterior is followed by motive, meaning a hidden or secret purpose: he had an ulterior motive - il avait un motif secret.

Usuel vs Usual

Usuel means ordinary, everyday, or common.
Usual is slightly different: it leans more toward typical or normal - habituel or courant.

Vent vs Vent

Vent is the noun wind.
Vent can refer to any of the following: un orifice, un conduit, un tuyau, une cheminée, un trou, une fente.

Vexé vs Vexed

Vexé means hurt, upset, or offended, while Vexed means angry - fâché.

Vie vs Vie

Vie is the French word for life: C'est la vie - That's life.
Vie means to struggle or fight: I struggled with him for the gun - J'ai lutté avec lui pour le pistolet.

Volatil(e) and Volatile vs Volatile

Volatil(e) means volatile when referring to a chemical. It can also mean fleeting: une valeur volatile - a fleeting value. Une volatile is a bird or other winged creature.
Volatile can only be translated by volatil(e) in the chemistry lab. A volatile situation - une situation explosive. A volatile person - une personne versatile.