Other
Derivation and Classification of Groups
This gives examples of classification of the differences between rotation and translation.
Wolfram Research
Wolfram Math World: Parallel Lines
A definition for parallel lines in two-dimensional and three-dimensional Euclidean space. The site also gives reference to skew lines and explains the difference between skew and parallel lines in three-dimensional space.
Varsity Tutors
Varsity Tutors: Hotmath: Algebra Review: Perpendicular and Parallel Lines
Find a quick, concise explanation of what perpendicular lines are. An example is given and clearly explained. Also, parallel lines are explained.
Oswego City School District
Regents Exam Prep Center: Parallel Through a Point
This step-by-step demonstration teaches students to construct a line parallel to another through a given point.
Physics Aviary
Physics Aviary: Practice Problems: Parallel Circuit
Determine the amount of current that is present in a parallel circuit.
National Council of Teachers of Mathematics
The Math Forum: Math to Build On: Crossing & Parallel Lines
A definition of parallel lines that draws a comparison to planes and provides drawings for examples.