  In this paper, we study the singular sets of $F$-subharmonic functions $u:
B_{2}(0^{n})\rightarrow\mathbf{R}$, where $F$ is a subequation. The singular
set $\mathcal{S}(u)\subset B_{2}(0^{n})$ has a stratification
$\mathcal{S}^{0}(u)\subset\mathcal{S}^{1}(u)\subset\cdots\subset\mathcal{S}^{k}(u)\subset\cdots\subset\mathcal{S}(u)$,
where $x\in\mathcal{S}^{k}(u)$ if no tangent function to $u$ at $x$ is
$(k+1)$-homogeneous. We define the quantitative stratification
$\mathcal{S}_{\eta,r}^{k}(u)$ and
$\mathcal{S}_{\eta}^{k}(u)=\cap_{r}\mathcal{S}_{\eta,r}^{k}(u)$.
  When homogeneity of tangents holds for $F$, we prove that
$dim_{H}\mathcal{S}^{k}(u)\leq k$ and $\mathcal{S}(u)=\mathcal{S}^{n-p}(u)$,
where $p$ is the Riesz characteristic of $F$. And for the top quantitative
stratification $\mathcal{S}_{\eta}^{n-p}(u)$, we have the Minkowski estimate
$\text{Vol}(B_{r}(\mathcal{S}_{\eta}^{n-p}(u)\cap B_{1}(0^{n})))\leq
C\eta^{-1}(\int_{B_{1+r}(0^{n})}\Delta u)r^{p}$.
  When uniqueness of tangents holds for $F$, we show that $S_{\eta}^{k}(u)$ is
$k$-rectifiable, which implies $\mathcal{S}^{k}(u)$ is $k$-rectifiable.
  When strong uniqueness of tangents holds for $F$, we introduce the
monotonicity condition and the notion of $F$-energy. By using refined covering
argument, we obtain a definite upper bound on the number of $\{\Theta(u,x)\geq
c\}$ for $c>0$, where $\Theta(u,x)$ is the density of $F$-subharmonic function
$u$ at $x$.
  Geometrically determined subequations $F(\mathbb{G})$ is a very important
kind of subequation (when $p=2$, homogeneity of tangents holds for
$F(\mathbb{G})$; when $p>2$, uniqueness of tangents holds for $F(\mathbb{G})$).
By introducing the notion of $\mathbb{G}$-energy and using quantitative
differentation argument, we obtain the Minkowski estimate of quantitative
stratification $\text{Vol}(B_{r}(\mathcal{S}_{\eta,r}^{k}(u))\cap
B_{1}(0^{n}))\leq Cr^{n-k-\eta}$.
