What's the difference between 母方 and 母系? The same question goes to 父方 and 父系


I saw these words a while ago but just now I decided to ask it here because I
didn't find the answer anywhere.

As the title says, I don't really know if there is a difference between
母方【ははかた】 X 母系【ぼけい】, and 父方【ちちかた】 X 父系【ふけい】as well.

The sentences I've come across are:

> 父方【ちちかた】の祖父【そふ】の米寿【べいじゅ】のお祝【いわ】いにマフラーを贈【おく】った。

and

> 母系【ぼけい】の祖母【そぼ】はその旧式【きゅうしき】のドレスを着る【きる】ことに固執【こしつ】する。




First, let me point out that your second example,

> 母系の祖母はその旧式のドレスを着ることに固執する。

is a very unnatural sentence. You could hardly say something like that, if not
never. When I searched 母系の祖母 I only found this example from [Tanaka
Corpus](http://www.edrdg.org/wiki/index.php/Tanaka_Corpus), which contains
many errors and should not always be deemed as authoritative Japanese usage
(see their disclaimer).

Instead you should always say:

> **父方** の祖父 _paternal grandfather_  
>  **母方** の祖母 _maternal grandmother_

Generally speaking, 母方／父方 is what you call your mother/father's house or
kinship from your perspective, so you are mentally facing your parents'
direction. 母系／父系 means _matriline_ / _patriline_ , which is a line of descent
passed down from your ancestors to you (they are genealogical terms). For this
reason, 母系／父系 is usually used to describe hereditary, or inheritance matters,
that conceptualized in descending order, not when you call your grandparents.




First, let me point out that your second example,

> 母系の祖母はその旧式のドレスを着ることに固執する。

is a very unnatural sentence. You could hardly say something like that, if not
never. When I searched 母系の祖母 I only found this example from [Tanaka
Corpus](http://www.edrdg.org/wiki/index.php/Tanaka_Corpus), which contains
many errors and should not always be deemed as authoritative Japanese usage
(see their disclaimer).

Instead you should always say:

> **父方** の祖父 _paternal grandfather_  
>  **母方** の祖母 _maternal grandmother_

Generally speaking, 母方／父方 is what you call your mother/father's house or
kinship from your perspective, so you are mentally facing your parents'
direction. 母系／父系 means _matriline_ / _patriline_ , which is a line of descent
passed down from your ancestors to you (they are genealogical terms). For this
reason, 母系／父系 is usually used to describe hereditary, or inheritance matters,
that conceptualized in descending order, not when you call your grandparents.

