There are several words in Spanish that are similar in English, but have a different meaning. Here are a few examples:

• actually is similar to Spanish actualmente; however, actualmente is better translated with e.g. currently, as actually actually means in reality. Confusing, eh?
• embarrassed is not the same as embarazada. A translation for embarrassed could be apenado. In some situations it can be embarrassing to be embarazada, i.e. pregnant!
• realize should not be confused with Spanish realisar. When Mexican students use the English word realize, they normally use it meaning to say something like: to give an idea physical form. They mostly don't realize that realize also means that you become aware of something.
• approve is sometimes confused with aprobar:"Teacher, did I approve the exam?" aprobar means pass as in 'pass an exam', whereas approve means to agree to something.
• eventually is not the same as eventual(mente). Eventually could be translated with finalmente, as it means: in the end, in the long run. The Spanish cognate eventual is in meaning similar to English temporary or conditional.
• Mexican students often use the word career to refer to their studies (Spanish carrera):"When I finish my career, I want to go to United States (sic)". Career, refers to professional work. When you finish your career you'll be an old person!
• lecture is not the same as lectura. A lecture is a talk about a particular topic. A translation for lectura could be reading or simply text.
• apartment in Spanish is departamento; department is also departamento. Therefore it is understandable that speakers of Spanish frequently use department when referring to an apartment.
• Spanish speakers often confuse by and for in passive voice. The reason is that they use por and that looks and sounds like for.
• another 'false friend' is try with Spanish tratar, as in this sentence:"the movies tries with the problems of a strange man," or:"in business, you have to try with people." Again, the confusion is understandable. In Spanish you would use tratar in both cases; however, in English you might consider using is about and deal with respectively.
• Speakers of Spanish also tend to confuse win with ganar. Teachers frequently read or here things like:"They win a lot of money," instead of "They make/earn a lot of money." You win money in the lottery. Making or earning money refers to your salary/ income.
  Now that we're talking about win, we should also mention the difference between win and beat. Here's how they should be used:
  América beat Guadalajara 9-0! (beat the opponent)
  América won the game (win the game)
  
• Politics/ Politician: When referring to the authorities, speakers of Spanish normally confuse Spanish politico(s) with English politics. A politician is a person who has a job in politics. Politician = politico. Politics refer to, say, the regulation of a country.
  
• Here's another good one: the other day I bought a bookcase and on the box it said: library with three shelves. Now, where's the mistake?
  The problem is that library is not the same as librero. Look:
  

  library = biblioteca
  bookstore = libreria
  bookcase = librero
  

• Compromise and compromiso aren't equivalents either. Compromiso should be translated with commitment. Compromise refers to making concessions to come to an agreement, a settlement.
  
• The word familiar exists both in English and Spanish; however, the meaning is completely different. Familiar in Spanish refers to a member of your family (in English you would use the word relative(s)). It's a noun. Familiar in English is an adjective and it means that you know something about something eg:
  - Are you familiar with Shakespeare's work?
  
• The Spanish word cientifico is both noun (profession) and adjective. Therefore students often use the word scientific to refer to the person:
  He is a famous scientific.
  However, scientist should be used to refer to the person:
  He is a famous scientist.
  
• Parents only refers to your father and mother.
  parientes, on the other hand, refers to your extended family, cousins, uncles, aunts etc. Therefore, parientes is relatives in English.

There are many words that sound similar but have different meanings and are spelled differently. Then there are other words that even sound exactly the same, but are spelled differently and have different meanings. Here are some examples:

1) custom vs. costume:

Custom refers to repetitive, traditional activities e.g.
The celebration of the Day of the Dead is a typical Mexican custom.
A costume is something that you wear e.g.
The costumes in Shakespeare in Love are very well made.

2) loose vs. lose:

Loose is the opposite of tight. It's an adjective. Imagine Michael Jackson in Pavarotti's clothes.
Lose is a verb and refers to objects that have disappeared. Example:
"I can't find my wallet, I have lost it."

3) guy vs. gay

This one can cause a lot of confusion. The mistake normally occurs in writing only, because students know the difference in pronunciation between guy and gay. They also know the difference in meaning:

guy = boy/ young man as in: he's a very nice guy.
gay = homosexual (it used to mean something like: lively or bright, but that's old fashioned and common in the works of, say, Charles Dickens.

4) earn vs. win

The problem with these two is that they are both translated into Spanish with ganar. Thus, you get questions like: "How much do you win?" when referring to your salary. However, you win money in the lottery and you earn (or make) money at your job.

5) I am agree

A common error among Spanish speakers is the translation 'I am agree for Estoy de acuerdo. One should keep in mind that agree is a verb, whereas de acuerdo, as in estoy de acuerdo, is an adjective. Therefore, one should say:
- I agree
- He agrees
- We agree

And in past for example:

- I agreed

Here are some examples of 'Gringo' influence on our students:

- hackear
- deletear
- vacumear
- mailear
- inclusionar
- votear
- parkquear
- echar un speich

And a new English word:

- clonation (instead of cloning)

First of all, there's the problem in pronunciation. Spanish speakers tend to pronounce this and these the same. Therefore students frequently use only this in writing. They don't seem to realize that there is also a plural form. This may look very obvious, but it is a recurrent problem. Examples:
incorrect: "I think all this problems are related to poverty".
correct : "I think all these problems are related to poverty"
This is singular, whereas these is plural.

Definition: An adjective modifies a noun.

Students may know their adjectives, but the main problem is: where to place them in the sentence. The thing is, in Spanish you generally place the adjective after the noun. In English it's the opposite. A simple example:

Incorrect: A house beautiful.
Correct: A beautiful house.

Incorrect: This is a course very interesting.
Correct: This is a very interesting course.

Now something about adverbs:

Defenition: an adverbs modifies

a) an adjective
b) a verb
c) another adverb

Examples:

a) She has an incredibly beautiful voice!
b) He always drives fast.
c) He always drives terribly fast.

How can you know when you have to use either an adjective or an adverb? Simple: look at the word that needs to be modified. Is it a noun, then use an adjective. Is it a verb, adjective or adverb, then use an adverb.

It's easy to distinguish adverbs from adjectives: they generally and with -ly, e.g:
He is a bad student: bad is an adjective; it modifies the noun student.
He sings badly: badly is an adverb; it modifies the verb sings.

There are some exceptions of course, for example:

adjective          adverb

fast               fast
hard               hard

Note: hardly also exists, but it has a different meaning, i.e. almost not.
Look at these sentences: do you feel the difference?:
a) He works hard.
b) He hardly works.