# Subequation Numbering and placement arrangements

    \begin{subequations}
\renewcommand\arraystretch{1.33} % or some other suitable value
\begin{flalign}
{}_{\mathrm{L}}^{}\mathbf{M} &\equiv
\begin{bmatrix}
{}_{\mathrm{L}}^{}\mathbf{M}^{\mathrm{f}}_{ii} & 0 & 0 \\
0 & {}_{\mathrm{L}}^{}\mathbf{M}^{\mathrm{fs}}_{cc} & 0 \\
0 & 0 &{}_{\mathrm{L}}^{}\mathbf{M}^{\mathrm{s}}_{ii} \,
\end{bmatrix}, \label{fsi_mass_mat}\\
\mathbf{C} &\equiv
\begin{bmatrix}
\mathbf{C}^{\mathrm{f}}_{ii} & \mathbf{C}^{\mathrm{f}}_{ic} & 0 \\
\mathbf{C}^{\mathrm{f}}_{ci} & \mathbf{C}^{\mathrm{f}}_{cc} & 0 \\
0 & 0 & \mathbf{C}^{\mathrm{s}}_{ii} \,
\end{bmatrix},\label{fsi_diffusion_mat} \\
\mathbf{G} &\equiv
\begin{bmatrix}
\mathbf{G}^{\mathrm{f}}_{i} \\
\mathbf{G}^{\mathrm{f}}_{c} \\
0
\end{bmatrix}, \label{fsi_divergence_mat} \\
\mathbf{q(u)} &\equiv
\begin{Bmatrix}
0 \\
\mathbf{q}^{\mathrm{s}}_{c}(\mathbf{u}^\mathrm{s}) \\
\mathbf{q}^{\mathrm{s}}_{i}(\mathbf{u}^\mathrm{s})
\end{Bmatrix}, \label{fsi_internal_force_vec_str}\\
\mathbf{N} &\equiv
\begin{Bmatrix}
\mathbf{N}^{\mathrm{f}}_{i} \\
\mathbf{N}^{\mathrm{f}}_{c} \\
0
\end{Bmatrix}, \label{fsi_convection_vec} \\
\mathbf{g} &\equiv
\begin{Bmatrix}
\mathbf{g}^{\mathrm{f}}_{i}  \\
\mathbf{g}^{\mathrm{fs}}_{c} \\
\mathbf{g}^{\mathrm{s}}_{i}
\end{Bmatrix}, \label{fsi_external_force_vec} \\
\mathbf{a} &\equiv
\begin{Bmatrix}
\mathbf{a}^{\mathrm{f}}_{i} \\
\mathbf{a}^{\mathrm{fs}}_{c} \\
\mathbf{a}^{\mathrm{s}}_{i}
\end{Bmatrix}, \label{fsi_accl_vec} \\
\mathbf{v} &\equiv
\begin{Bmatrix}
\mathbf{v}^{\mathrm{f}}_{i} \\
\mathbf{v}^{\mathrm{fs}}_{c} \\
\mathbf{v}^{\mathrm{s}}_{i}
\end{Bmatrix}, \label{fsi_vel_vec} \\
\mathbf{u} &\equiv
\begin{Bmatrix}
\ast \\
\mathbf{u}^{\mathrm{fs}}_{c} \\
\mathbf{u}^{\mathrm{s}}_{i}
\end{Bmatrix}, \label{fsi_disp_vec}\\
\mathbf{p} &\equiv  \mathbf{p}^{\mathrm f}, \label{fsi_pressure_vec}\\
{}_{\mathrm{L}}^{}\mathbf{M}^{\mathrm {fs}}_{cc} &\equiv {}_{\mathrm{L}}^{}\mathbf{M}^{\mathrm {f}}_{cc}+{}_{\mathrm{L}}^{}\mathbf{M}^{\mathrm {s}}_{cc}, \label{FSI_mass_mat_coupled}
\end{flalign}
\end{subequations}


Hi members and @Mico : Actually, I am looking for the type of numbering and arrangement of subequations as shown in the attached Figure. At present, I get the numbering as (4.45a), (4.45b), (4.45c), (4.45d), (4.45e)...etc, shown in Top Figure. Eq.(4.45j) and (4.45k) runs outside the page. I want to change the numbering style only for this set of subequations like (4.45 a-k), as shown in the below figure (Last). Thank you.

• It is easy to emulate this numbering, but you will lose cross-referencing to individual subequations. – Bernard Oct 24 '18 at 8:13
• @Bernard, Please let me know how to do. I am desperately looking it. I need to cross-refer eq.(4.45i), however I will write the eqn number while cross-referring eq.(4.45i). Thank you – Prakash Oct 24 '18 at 8:35

As @Bernard has pointed out in a comment, (a) your numbering system can be achieved without making use of a subequations environment and (b) one will necessarily lose the ability to cross-reference individual subequations.

For the following screenshot, I use a a single align environment, \notag directives for rows 1, 2, and 3, and a \tag directive to customize the appearance of the equation "number" in the final row. The main change, relative to the code you posted, is that I've replaced 7 of the 10 end-of-row \\ (line-break) instructions with \quad. In addition, I removed the 11 existing \label statements since you don't want to output individual subequation numbers.

Speaking for myself, I cannot see a valid reason for maintaining that the full group of equations consists of 11 separate subequations if you're not also willing to make it easy for your readers to identify which subequation might, e.g., correspond to the letter "i", i.e., constitute the 9th subequation. It would be much better for your readers if you used a single gather environment and a single equation number for all 11 equations. If you really need to cross-reference one of the subequations, you'd just write something like "... as can be seen in the expression for $\mathbf{g}$ in equation \eqref{<use the appropriate label>}, ....

\documentclass{report}
\usepackage{amsmath}
\allowdisplaybreaks
% handy shortcut macro:
\newcommand\LMmat[1][]{{}_{\mathrm{L}\mkern-2mu}^{}\mathbf{M}^{\mathrm{#1}}}

\begin{document}
\setcounter{chapter}{4}\setcounter{equation}{44} % just for this example

\begingroup % localize scope of the following instruction
\renewcommand\arraystretch{1.33} % or some other suitable value
\begin{align}
\refstepcounter{equation}
\LMmat &\equiv
\begin{bmatrix}
\LMmat[f]_{ii} & 0 & 0 \\
0 & \LMmat[fs]_{cc} & 0 \\
0 & 0 & \LMmat[s]_{ii} \,
\mathbf{C} \equiv
\begin{bmatrix}
\mathbf{C}^{\mathrm{f}}_{ii} & \mathbf{C}^{\mathrm{f}}_{ic} & 0 \\
\mathbf{C}^{\mathrm{f}}_{ci} & \mathbf{C}^{\mathrm{f}}_{cc} & 0 \\
0 & 0 & \mathbf{C}^{\mathrm{s}}_{ii} \,
\mathbf{G} \equiv
\begin{bmatrix}
\mathbf{G}^{\mathrm{f}}_{i} \\
\mathbf{G}^{\mathrm{f}}_{c} \\
0
\end{bmatrix},  \notag\\
\mathbf{q(u)} &\equiv
\begin{Bmatrix}
0 \\
\mathbf{q}^{\mathrm{s}}_{c}(\mathbf{u}^\mathrm{s}) \\
\mathbf{q}^{\mathrm{fs}}_{i}(\mathbf{u}^\mathrm{s})
\mathbf{N} \equiv
\begin{Bmatrix}
\mathbf{N}^{\mathrm{f}}_{i} \\
\mathbf{N}^{\mathrm{f}}_{c} \\
0
\mathbf{g} \equiv
\begin{Bmatrix}
\mathbf{g}^{\mathrm{f}}_{i}  \\
\mathbf{g}^{\mathrm{fs}}_{c} \\
\mathbf{g}^{\mathrm{fs}}_{i}
\end{Bmatrix},  \notag \\
\mathbf{a} &\equiv
\begin{Bmatrix}
\mathbf{a}^{\mathrm{f}}_{i} \\
\mathbf{a}^{\mathrm{fs}}_{c} \\
\mathbf{a}^{\mathrm{fs}}_{i}
\mathbf{v} \equiv
\begin{Bmatrix}
\mathbf{v}^{\mathrm{f}}_{i} \\
\mathbf{v}^{\mathrm{fs}}_{c} \\
\mathbf{v}^{\mathrm{fs}}_{i}
\mathbf{u} \equiv
\begin{Bmatrix}
\ast \\
\mathbf{u}^{\mathrm{fs}}_{c} \\
\mathbf{u}^{\mathrm{fs}}_{i}
\end{Bmatrix}, \notag\\
\LMmat[fs]_{cc} \equiv \LMmat[f]_{cc} + \LMmat[s]_{cc}\,.
\tag{\arabic{chapter}.\arabic{equation}a--k}
\label{eq:11subequations}
\end{align}
\endgroup

\noindent
A cross-reference to equations \eqref{eq:11subequations}.

%%%%%
\medskip\hrule\medskip

\begingroup % localize scope of the following instruction
\renewcommand\arraystretch{1.33} % or some other suitable value
\begin{gather}
\LMmat \equiv
\begin{bmatrix}
\LMmat[f]_{ii} & 0 & 0 \\
0 & \LMmat[fs]_{cc} & 0 \\
0 & 0 & \LMmat[s]_{ii} \,
\mathbf{C} \equiv
\begin{bmatrix}
\mathbf{C}^{\mathrm{f}}_{ii} & \mathbf{C}^{\mathrm{f}}_{ic} & 0 \\
\mathbf{C}^{\mathrm{f}}_{ci} & \mathbf{C}^{\mathrm{f}}_{cc} & 0 \\
0 & 0 & \mathbf{C}^{\mathrm{s}}_{ii} \,
\mathbf{G} \equiv
\begin{bmatrix}
\mathbf{G}^{\mathrm{f}}_{i} \\
\mathbf{G}^{\mathrm{f}}_{c} \\
0
\end{bmatrix},  \notag \\
\mathbf{q(u)} \equiv
\begin{Bmatrix}
0 \\
\mathbf{q}^{\mathrm{s}}_{c}(\mathbf{u}^\mathrm{s}) \\
\mathbf{q}^{\mathrm{fs}}_{i}(\mathbf{u}^\mathrm{s})
\mathbf{N} \equiv
\begin{Bmatrix}
\mathbf{N}^{\mathrm{f}}_{i} \\
\mathbf{N}^{\mathrm{f}}_{c} \\
0
\mathbf{g} \equiv
\begin{Bmatrix}
\mathbf{g}^{\mathrm{f}}_{i}  \\
\mathbf{g}^{\mathrm{fs}}_{c} \\
\mathbf{g}^{\mathrm{fs}}_{i}
\end{Bmatrix},  \notag  \\
\mathbf{a} \equiv
\begin{Bmatrix}
\mathbf{a}^{\mathrm{f}}_{i} \\
\mathbf{a}^{\mathrm{fs}}_{c} \\
\mathbf{a}^{\mathrm{fs}}_{i}
\mathbf{v} \equiv
\begin{Bmatrix}
\mathbf{v}^{\mathrm{f}}_{i} \\
\mathbf{v}^{\mathrm{fs}}_{c} \\
\mathbf{v}^{\mathrm{fs}}_{i}
\mathbf{u} \equiv
\begin{Bmatrix}
\ast \\
\mathbf{u}^{\mathrm{fs}}_{c} \\
\mathbf{u}^{\mathrm{fs}}_{i}
\end{Bmatrix}, \notag  \\