improvement suggestion: 'dictionary' functionality
it's nice to have the dictionary that will show you the translation of a word in duolingo, but I think it could be improved by including the base form of the verb as well as the displayed word - e.g. if I tap on 'escribo' in Spanish, then display both 'I write' but also display: from 'escribir - to write'.
For nouns, similarly, if you tap on a plural noun, include the singular form - and - PLEASE include the gender - i.e. if I tap on 'cartas' in 'escribo cartas' - also display 'from: la carta'. (obviously, in many sentences, the gender is already visible - but many sentences don't).
Those are excellent suggestions. I hope they can be incorporated. At the moment I am compiling my own list but having it in front of you or in the form of a list that didn't drop you out of the lesson would be great help.