A word for when you only understand a language in its written form

Is there a specific word to express when you only understand the written form of a language?

For instance: I can read Portuguese, but I can't understand it when it's spoken to me.

Presumably you want a word to describe a non-native or learner of the language. For Europeans learning other European languages (where the writing is in the Roman or Cyrillic alphabet and learning to read is trivial in comparison to speak and listen), you would say that a person has

having reading proficiency

in the language. For a single word adjective, I don't think there's a wod for any particular ability like 'speakability' or 'readability' (that means what you want it to mean).

For languages where the accepted writing system takes much more study like Chinese or Japanese, most people learn those languages academically where the proficiency in both go at about the same rate (it's almost like learning two different languages at the same time, spoken and written).

For the other side, for native speakers, there is only the issue of whether they can read their own language and for that

literate

captures the idea.

'Literate' could also work for the non-native learner, but even though intended for only the reading skill, might be misunderstood for 'well-educated' in the language, meaning both able to read -and- speak well.

You will have to coin a new term. I suggest

solumliterate - literacy without other language ability

Similarly, for someone with speaking ability but not literacy you could say

solumlingual - speaking ability without literacy

which is better than "illiterate" which is a pejorative these days. You could also say

solumnumerate - numeracy without literacy or spoken linguistic ability

as in "until recently computers were solumnumerate".

The "solum" is from the Latin "solum" when used as "only" or "merely"

How about non-aurally fluent?