# Is the zero matrix in reduced row echelon form?

Is this matrix in reduced row echelon form? $3\times3$ matrix is:

0 0 0
0 0 0
0 0 0


I can say for other matrices but this one without 1s confuses me. Are $1$s optional in reduced row echelon form? I think they aren't. What do you think?

• What do you mean by "Are ones optional"? – 5xum Nov 17 '15 at 22:30
• @5xum Typically, RREF contains some 1s. The OP wants to know if it has to be that way. – user147263 Nov 17 '15 at 22:32
• I mean to say, are 1s that appear in reduced row echelon form optional? Will it be still reduced row echelon if I have not a single 1 in matrix. – user4904589 Nov 17 '15 at 22:33