The biggest question for me is always whether I can accurately call myself fluent in Spanish, given that I don't have complete mastery of the language. I can express myself in speech and writing pretty well on just about any subject, and read magazines and listen to newscasts without much trouble. But I definitely make my share of grammatical errors, and don't ask me to read Gabriel García Márquez in the original or interpret the rapidly spoken street Spanish in Mexico.
On the other hand, I consider each of my foreign-born coworkers to be fluent in English, and yet their use of the language rarely ventures outside the present indicative. The resumé guides I've read say not to call yourself fluent in a language unless you're willing to conduct the interview in it, which is probably a decent rule of thumb. With that in mind, I ended up listing my abilities as follows:
- Fluent: English, Spanish
- Functional: German, Taiwanese
- Basic: Mandarin
In the end, I probably didn't need to stress out so much over this section. In engineering, the lingua franca is undoubtedly English, and the lack of a huge semiconductor industry presence in Spanish-speaking countries probably renders my proficiency in that language---however one defines it---irrelevant. Nonetheless, I look forward to the day when I can place all my languages in the "fluent" category without any hint of deception.