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The meaning of most words is not learned through their definitions. When I say "Jack is walking", no one will ask me to define "Jack", to define "is" or to define "walking". Even in pure math, if I say "The set exists", no mathematician will ask me to define "The", to define "set" or to define "exists". The meaning of most words is learned gradually, through examples. (Artificial neural networks in machine learning also learn through examples, but humans usually need much smaller number of examples to learn it efficiently.)

The word

1. In classical mechanics, the particle position as a function of time ##x(t)## is ontic. Its Fourier transform ##\tilde{x}(\omega)## is not ontic.

2. In classical mechanics, anything that can

3. In classical mechanics, quantities that cannot be directly derived from ##x(t)## are not ontic. For example, mass ##m##, momentum ##p##, force ##F## and Lagrangian ##L(x,\dot{x})## are not ontic.

4. A classical wave ##\phi(x,t)## is ontic. Its spatial Fourier transform ##\tilde{\phi}(k,t)## is not ontic.

From those examples, one can use intelligent extrapolation to determine whether many other concepts in classical physics are ontic or not. (But in some cases it may not be obvious, so we may have have different interpretations of classical physics. That's particularly true in the theory of relativity.)

When one grasped the meaning of "ontic" in classical physics, one can start to think and talk about "ontic" in quantum physics.

The word

*ontic*is one such word. The meaning of "ontic" is somewhat similar to "real", but "ontic" has a narrower meaning. There is no precise definition, but it can be learned through examples. Here are some examples:1. In classical mechanics, the particle position as a function of time ##x(t)## is ontic. Its Fourier transform ##\tilde{x}(\omega)## is not ontic.

2. In classical mechanics, anything that can

*directly*be derived from ##x(t)## is ontic. The meaning of "directly" also has to be learned through examples. For instance, the velocity ##\dot{x}(t)## and acceleration ##\ddot{x}(t)## are directly derived from ##x(t)##. The momentum ##p(t)=m\dot{x}(t)## and the force ##F(x)## are not directly derived from ##x(t)##.3. In classical mechanics, quantities that cannot be directly derived from ##x(t)## are not ontic. For example, mass ##m##, momentum ##p##, force ##F## and Lagrangian ##L(x,\dot{x})## are not ontic.

4. A classical wave ##\phi(x,t)## is ontic. Its spatial Fourier transform ##\tilde{\phi}(k,t)## is not ontic.

From those examples, one can use intelligent extrapolation to determine whether many other concepts in classical physics are ontic or not. (But in some cases it may not be obvious, so we may have have different interpretations of classical physics. That's particularly true in the theory of relativity.)

When one grasped the meaning of "ontic" in classical physics, one can start to think and talk about "ontic" in quantum physics.

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