What's $\mathbb{R}$ doing in the definition of a metric space?
54685
Defining metrics as a function to something other than the reals.
61220
What does "$\mathbb{F^n}$ is a vector space over $\mathbb{F}$" mean?
140472
Is the space $\mathbb{N}$ is a baire spaces ? yes/No
56728
Question about limit points of a Subset of $\mathbb{R}$
35305
Why is $\mathbb{R}^2$ not a subset and /or a subspace of $\mathbb{R}^3$?
128598
How to prove this is a metric?
82333
let $(X,d)$ be a metric space. How I can show that any finite subset of $X$ is closed.
151425
Does $\mathbb{R}^n$ have a real vector space structure with dimension other than $n$?
104413
Is the exponential of $-d$ a positive definite kernel for a general metric space $(X, d)$?
73368
Does this proof that every open set in a metric space is a union of open balls use the axiom of choice?
80274
What is the "topology induced by a metric"?
113688
Is Topological Space a Metric Space?
126944
Metric spaces problem
16892
Reference request: product Borel $\sigma$-algebra of non-separable metric spaces
146485
Prove that the product space is a metric space.
66550
Cardinality of separable metric spaces
52014
Showing $(C[0,1], d_1)$ is not a complete metric space