Expiation and propitiation are similar but expiation does not carry the implication of dealing with wrath, of appeasing it through a sacrifice. Generally speaking, propitiation cancels sin and deals with God's wrath. Expiation is simply the cancellation of sin. It is synonymous with trust. Fast, Fasting Depriving oneself of food for a period of time for a specific purpose, often spiritual.
Fellowship implies sharing common interests, desires, and motivations.
Fellow requires that time be spent with another communicating, caring, etc. It carries with it a hint of intimacy. As Christians we fellowship with one another because of our position in Christ, because we are all redeemed and share an intimate personal knowledge of Jesus. The Greek word for fellowship is koinonia . This is where we get the term the communion supper.