Alt text should primarily describe what's genuinely in an image, but where a related term fits naturally, it can add useful context without compromising accuracy.
Accuracy Comes First, Every Time
Alt text exists to describe the actual image content; a related term should only be included if it genuinely, accurately applies to what's shown.
Avoid Forcing Unrelated Terms Into Descriptions
An alt text description stretched to include a related term that doesn't actually apply to the image undermines both accessibility and credibility.
Use Surrounding Content to Guide Natural Inclusion
When a related term genuinely fits an image's context within the surrounding content, working it in naturally is reasonable; forcing it isn't.
Next step: Use the LSI Tool to identify related terms that might genuinely and accurately apply to your image content.