It seems like your question is incomplete. However, I can provide some common classifications of systems. Two types of systems often referenced in various fields include:
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Open Systems: These systems exchange energy, matter, or information with their environment. Examples include ecosystems, organizations, and the human body.
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Closed Systems: These systems do not exchange matter with their surroundings, although they may exchange energy. An example of a closed system is a sealed container of gas.
If you were referring to a different classification or specific context (like in technology, mathematics, etc.), please provide more details.