Sentence:  The **f layers are stacked <WSD>normal</WSD> to the [ 111 ] axis with the lower oxygens of one layer directly above the upper oxygens of the neighboring lower layer , in such a manner that the repeat is every three layers . 
Meaning of the word marked with <WSD> tags:  conforming with or constituting a norm or standard or level or type or social norm; not abnormal