Vocabulary
• Reproduction,: This means the living organisms' method to make offspring.
,
• Homeostasis,: This means the living organisms' method to maintain their body.
,
• Energy Use,: This means the living organisms' method to use energy in form of ATP and energy consumption.
,
• Growth/Development,: This means the living organisms' method to grow and mature.
,
• Response to Stimuli,: This means the living organisms' response to external factors.
Application
Together, when we combine all the defined vocabulary above, these are the characteristics of a living organism. All living organisms must display these characteristics, or they are not classified as "alive." Reproduction, Homeostasis, Energy Use, Growth/Development, and Response to Stimuli are all things necessary for a living organism to survive and adapt to its environment.
Answer
Therefore, we know that something is alive if they display signs of reproduction, homeostasis, energy use, growth/development, and response to stimuli.