Multilingual NLP

#The Problem

English has billions of labeled examples. Urdu has thousands. Maithili has almost none. Any practical NLP system that serves a global audience has to work on the long tail of languages where task-specific training data does not exist.

Multilingual models solve this by training one model on many languages simultaneously. The shared representation lets the model transfer skills learned in high-resource languages to low-resource ones. Fine-tune the model on English sentiment analysis, and it produces surprisingly good sentiment predictions on Urdu out of the box. That is zero-shot cross-lingual transfer, and it has reshaped how NLP ships to the world.

This lesson names the tradeoffs, the canonical models, and the one decision that trips up teams new to multilingual work: picking a source language for transfer.