Semantic search (contextual, conversational) – aka previously impacted by the Hummingbird update in 2013 – has a new sheriff in town. RankBrain is an improved artificial intelligence / mathematical processing toolset allowing Google to connect massive amounts of data in arrays or vectors so when someone does a search query Google can interpret the intent better than every before. Read more here, here and here.
Currently the third most important ranking signal (and processing up to 15% of all search queries a day), RankBrain will continue to improve and increase in overall influence on search ranking. Read more here.