Diffusion (noun). the act of diffusing, or the state of being diffused; a spreading; extension; dissemination; circulation; dispersion. Diffusion (noun). the act of passing by osmosis through animal membranes, as in the distribution of poisons, gases, etc., through the body.
Learner's definition of EXCITEMENT. 1. [noncount] : a feeling of eager enthusiasm and interest : the state of being excited. Our excitement was building/growing/mounting as the end of the game approached. His hands shook with excitement. The child cried out in excitement.
The definition of excited is  someone or something that has enthusiasm or is emotionally aroused. An example of excited is a barking dog when the mailman comes to the door.