Provides a well-written, clear and complete description of the topic, as described in Wikipedia:Article development. It should be of a length suitable for the subject, appropriately structured, and be well referenced by a broad array of reliable sources. It should be well illustrated, with no copyright problems. Only minor style issues and other details need to be addressed before submission as a featured article candidate. See the A-Class assessment departments of some of the larger WikiProjects (e.g. WikiProject Military history).
The article reasonably covers the topic, and does not contain obvious omissions or inaccuracies. It contains a large proportion of the material necessary for an A-Class article, although some sections may need expansion, and some less important topics may be missing.
The article has a defined structure. Content should be organized into groups of related material, including a lead section and all the sections that can reasonably be included in an article of its kind.
The article is reasonably well-written. The prose contains no major grammatical errors and flows sensibly, but it does not need to be "brilliant". The Manual of Style does not need to be followed rigorously.
The article contains supporting materials where appropriate. Illustrations are encouraged, though not required. Diagrams and an infobox etc. should be included where they are relevant and useful to the content.
The article is better developed in style, structure and quality than Start-Class, but fails one or more of the criteria for B-Class. It may have some gaps or missing elements; need editing for clarity, balance or flow; or contain policy violations such as bias or original research. Articles on fictional topics are likely to be marked as C-Class if they are written from an in-universe perspective.
The article has a usable amount of good content but is weak in many areas. Quality of the prose may be distinctly unencyclopedic, and MoS compliance non-existent; but the article should satisfy fundamental content policies such as notability and BLP, and provide sources to establish verifiability. No Start-Class article should be in any danger of being speedily deleted.