Likelihood of confusion is influenced by similarities, seniority and market environment:
Similarity between two trademarks in regard to their appearance, sound, and/or meaning or similarity between goods or services (e.g., breakfast cereal vs. breakfast bars).
The strength of senior trademark or the likelihood that a senior trademark will expand into the product category of a junior trademark. Trademarks that are very well known can be damaging even if they are used in unrelated areas.
The intended adoption by a junior trademark of a senior trademark to knowingly benefit from its reputation.
The importance that buyers give to the trademark for specific goods and the overlap of marketing environment and channels of trade. Are both trademarks presented to the market by the same channels or are the products sold by totally different channels?