The difference between blogs and wikis

Blogs and Wikis are a world of difference, and in my opinion, cannot be logically compared as the same.
Blogs are managed by most often one person, sometimes multiple owners called admins run the site to keep it in the most updated fashion possible. You can not alter posts, but you may comment below them. If you are the owner or admin you have full power to do whatever, whether it be altering, deleting, or creating new posts. Blogs are used to share information to a group of people, but not so much for a group of people to give input.
Wikis are in a very vague way similar to blogs. They are online, and available to share information. Wikis are only view able by someone who can also manage the site too, or an admin. An admin cannot alter or delete anyone else's posts or discussion threads but can comment on them, and create, delete, or alter their own posts, and discussion threads easily.
There is so much difference between a wiki and a blog, I'm unsure in what world they're connected so closely.