Décevoir vs Deceive

Décevoir means to disappoint: Il va te décevoir - He's going to disappoint you.
To deceive means to deliberately trick or lead someone astray: I didn't mean to deceive you - Je n'avais pas l'intention de te tromper.

Défaut vs Default 

Défaut is a flaw, fault, drawback, or lack.
Default is un défaut in judiciary proceedings. To default = manquer à ses engagements or prendre une valeur par défaut.

Défi vs Defy

Défi is a noun: defiance or challenge.
Defy is the verb défier or braver.

Défiler vs Defile

Défiler means to march past: les visiteurs défilaient devant le musée - the visitors marched past the museum and it can mean to unthread (a needle): Je dois défiler l'aiguille - I need to unthread the needle.
To defile is to dirty or deface something or to ruin someone's name: It's wrong to defile a great man - C'est mal de profaner un grand homme.

Délai/Délayer vs Delay

Délai is a time limit or deadline: dans un délai de 15 jours - within two weeks. Délayer means to water down or thin down, as in cooking or mixing paint.
Delay has a slightly negative connotation - it indicates that the time was unexpected and is usually translated by "retard" : They arrived with an hour's delay - Ils sont arrivés avec une heure de retard.

Demander vs Demand

Demander means to ask for: Il m'a demandé de chercher son pull - He asked me to look for his sweater. However, the French noun demande does correspond to the English noun demand.
(to) Demand is usually translated by exiger: He demanded that I look for his sweater - Il a exigé que je cherche son pull.

Détail vs Detail 

Détail is a semi-false cognate. In addition to detail, it can refer to retail.
Detail means détail or renseignements.

Dire vs Dire

Dire means to say or to tell.
Dire is an adjective which means affreux, terrible, or extrême.

Divers vs Divers

Divers means diverse, varied, or several.
Divers is the plural of diver - plongeur.

Douche vs Douche

une Douche is a shower, while Douche refers to a method of cleaning a body cavity with air or water: lavage interne.

Draguer vs Drag 

Draguer informally means to flirt. Formally, it means to fish with a dragnet or to dredge.
Drag means traîner or tirer.

Émergence vs Emergency 

Émergence is the equivalent of the English words emergence or source.
Emergency is un cas urgent or un imprévu.

Engagement vs Engagement

Engagement is any agreement, commitment, promise, or obligation.
Engagement usually refers to les fiançailles.

Entrée vs Entrée

Entrée is another word for hors-d'oeuvre; an appetizer.
Entrée refers to the main course of a meal: le plat principal.

Envie vs Envy

Avoir envie de means to want or to feel like something: Je n'ai pas envie de travailler - I don't want to work (feel like working). The verb envier, however, does mean to envy.
Envy means to be jealous or desirous of something belonging to another. The French verb is envier: I envy John's courage - J'envie le courage à Jean.

Étiquette vs Etiquette 

Étiquette is a semi-false cognate. In addition to etiquette or protocole, it can be a sticker or label.
Etiquette can mean étiquette, convenances, or protocole.

Éventuel vs Eventual

Éventuel means possible: le résultat éventuel - the possible outcome.
Eventual describes something that will happen at some unspecified point in the future; it can be translated by a relative clause like qui s'ensuit or qui a résulté or by an adverb like finalement.

Éventuellement vs Eventually

Éventuellement means possibly, if need be, or even: Vous pouvez éventuellement prendre ma voiture - You can even take my car / You can take my car if need be.
Eventually indicates that an action will occur at a later time; it can be translated by finalement, à la longue, or tôt ou tard : I will eventually do it - Je le ferai finalement / tôt ou tard.

Évidence vs Evidence 

Évidence is a semi-false cognate. In addition to evidence or the facts, it can mean obviousness, an obvious fact, or prominence.
Evidence means évidence, témoignage, or preuve.

Évident vs Evident

Évident usually means evident or obvious, but there is a familiar expression that always catches me: ce n'est pas évident - it's not that simple.
Evident means évident or manifeste.

Expérience vs Experience

Expérience is a semi-false cognate, because it means both experience and experiment: J'ai fait une expérience - I did an experiment. J'ai eu une expérience intéressante - I had an interesting experience.
Experience can be a noun or verb refering to something that happened. Only the noun translates into expérience : Experience shows that ... - L'expérience démontre que... He experienced some difficulties - Il a rencontré des difficultés.

Expérimenter vs Experiment

Expérimenter is a semi-false cognate. It is equivalent to the English verb, but also has the added sense of to test an apparatus.
Experiment as a verb means to test hypotheses or ways of doing things. As a noun, it is equivalent to the French word expérience (see above).

Fabrique vs Fabric 

Fabrique is a factory. De bonne fabrique means good workmanship.
Fabric is equivalent to tissu or étoffe. When speaking figuratively, e.g., the fabric of society, the French word is structure.

Facilité vs Facility

Facilité means ease, easiness, ability, or aptitude.
Facility is a semi-false cognate. It usually refers to a structure that serves a particular function, although it can mean easiness, aptitude, etc.

Façon vs Fashion

Façon means way, as in voilà la façon dont il procède - this is the way he does it. It can be translated by fashion when it is synonymous with way or manner, as in à ma façon - in my fashion or my way.
Fashion is a style or custom, usually in clothing: mode or vogue. For all of you apple pie eaters out there, now you know that à la mode really means in fashion.

Fastidieux vs Fastidious

Fastidieux means tedious, tiresome, or boring
Fastidious means attentive to detail or exacting: minutieux, méticuleux, tatillon.

Fendre vs Fend 

Fendre means to split or to chop.
Fend is se débrouiller, to fend off means parer or détourner.

Figure vs Figure

Figure is a semi-false cognate. It is the French word for face, but can also refer to an illustrated or mathematical figure.
Figure refers to numbers chiffres as well as to the form of a person's body: forme, silhouette.

File/Filer vs File 

File is a line or queue. Filer means to spin (e.g., cotton or thread) or to prolong.
File can refer to une lime (as well as the verb limer), un dossier, or un classeur (and the verb classer).

Film vs Film 

Film refers to a movie.
Film can mean un film as well as la pellicule.

Finalement vs Finally 

Finalement means eventually or in the end.
Finally is enfin or en dernier lieu.

Fond vs Fond 

Fond is a noun: bottom or back.
Fond is an adjective: to be fond of - aimer beaucoup, avoir de l'affection pour.

Format vs Format 

Format means size.
Format as a noun refers to présentation; as a verb it means formater or mettre en forme.

Formidable vs Formidable

Formidable is an interesting word, because it means "great" or "terrific"; almost the opposite of the English. Ce film est formidable ! - This is a great movie!
Formidable means dreadful or fearsome: The opposition is formidable - L'opposition est redoutable/effrayant.