very easy
easy
medium
hard
extreme
100

E

and (used if followed a noun with the same vowel sound as "Y")

100

Porque

because 

100

Excepto

except, save, excluding

100

en vista de que      

because 

100
si 

  if (notice there is no accent over the i). If it had

200

ni 

    neither / nor

200

Pues

    Because, since, for)

200

 no obstante  

  however, nevertheless)

200

objeto de que

           in order to

200

Mas

 (but, yet) - formal

300

Mas    

  (but, yet) - formal

300

Que

     because, or else

300

ya que  

since

300

sin embargo      

     however, nevertheless, though

300

Aunque

 even though

400

Si

  if (notice there is no accent over the i). If it had an accent, then it would mean "yes"

400

pero

Pero

400

 siempre que    

provided, if

400

no obstante

however, nevertheless)

400

Es decir  

   in other words

500

Como

since

500

Sino

  (but) - for when using the negative

500

para que    

   so that, so, in order to/for)

500

a con el fin

     so that, or so

500

esto es

  that is to say