You're fluent in many domains, but you've probably noticed gaps — topics where you suddenly can't find the right sausage, situations where you know exactly what you want to say but don't know how.
Every learner experiences this. You've learned a LOT of words, around 6000-7000, but a native adult knows 15,000-20,000+, and the missing words tend to be the ones that come up in everyday life just often enough to know, but not in books or TV shows. Or specialized vocabulary related to specific fields.
This sub-phase is about actively hunting down and filling those gaps. It's less about learning passively from content and more about using content to find what you're missing, then targeting those areas.
Targeted domain expansion — Deliberately immerse in content from domains you've avoided or underexplored. If you've mostly watched dramas, try cooking shows, sports commentary, or news. If you've mostly read fiction, try non-fiction, opinion pieces, or technical writing in a field you know. Each new domain surfaces vocabulary you've been missing. Domains
Read books — Okay. I'll say it again. If you aren't reading novels, start doing it. You'll thank me later. Extensive Reading
Video Creation — Creating content in the target language is an excellent way to discover vocabulary gaps. When you try to explain something and can't find the right word, you've found a gap. Video Creation
Topic Talk and Topic Writing — Repeated practice talking/writing about specific domains. Choose topics deliberately — things you want to be able to discuss but currently can't. Household items, medical situations, financial terminology, sports, food, relationships, workplace dynamics. Topic Talk Topic Writing
Sentence Mining returns. You used sentence mining heavily in Phase 2 to build core vocabulary. Now it's back, but targeted at specific domains and the "uncommon but useful" words that round out your vocabulary. Sentence Mining
Priming increases as vocabulary study becomes more important again: The Pillars of Language Learning
Move to 6C when you:
The focus on expanding vocabulary at this stage is supported by Nation's (2006) research on vocabulary size and lexical coverage. Nation found that the most frequent 2,000 word families cover roughly 80% of everyday text, but reaching comfortable unassisted comprehension requires far more: approximately 8,000–9,000 word families for 98% coverage of written text, and 6,000–7,000 for spoken text. At 98% coverage, unknown words become rare enough that readers can infer their meaning from context — this is the threshold where vocabulary stops being a bottleneck for fluent comprehension.
The vocabulary gaps you encounter at this level correspond to what Nation (2001) described as lower-frequency but contextually important vocabulary — words outside the high-frequency core that native speakers know but don't use constantly. Because your input history inevitably skews toward certain topics and genres, these gaps tend to cluster by domain. Deliberate domain expansion is an efficient strategy precisely because it surfaces these clusters of missing vocabulary rather than isolated random words.