When it comes to learning the basic shapes in German, Eva's got you covered with a video about exactly that:

Als Erstes haben wir hier einen Kreis.

First, we have a circle here.

Caption 13, Eva zeigt uns: Formen

 Play Caption

However, we often talk about shapes with a bit more nuance. For example, we might talk about spots and dots, or ovals rather than circles:

Alle Möbel mit roten Punkten gehören deiner Mama und die mit grünen gehören mir.

All of the pieces of furniture with red dots belong to your mother and those with green belong to me.

Caption 21, Mama arbeitet wieder Kapitel 4: Die Trennung

 Play Caption

Die Trainerschüler müssen die Hühner zum Beispiel dazu bringen, im Oval um zwei Kegel zu laufen.

The training students, for example, must get [their] chickens to walk around two cones in an oval.

Captions 24-25, Tierakademie Scheuerhof: Tiertrainer im Hühner-Seminar

 Play Caption

banner PLACEHOLDER

When we look at three-dimensional forms, there's a whole other set of vocabulary to learn. The word for a cube is actually der Kubus, but people describing objects will often use der Würfel, which is also the word you use for dice. 

Eine Masse von eineinhalb Sonnen, gepresst in eine Kugel mit gerade mal zehn Meilen Durchmesser.

A mass of one and a half suns pressed into a sphere with only a ten-mile diameter.

Captions 20-21, Unser Universum Sternengeburt: Das Leben nach dem stellaren Tod

 Play Caption

Wir haben hier fünfhundert Gramm Mehl, einen ganzen Würfel Hefe.

We have here five hundred grams of flour here, a whole cube of yeast.

Captions 8-9, Bundesländer und ihre Rezepte: Bayern

 Play Caption

Even though most patterns are repetitions of certain shapes, most of the words don't relate to the original forms. This makes sense, because even if a stripe is technically a long, thin rectangle, we don't perceive it as such. 

Oh, das Muster und... und diese Farben! Es ist wirklich überwältigend, wirklich!

Oh, the pattern and... and these colors! It is really overwhelming, really!

Caption 41, Märchen - Sagenhaft: Des Kaisers neue Kleider

 Play Caption

Die Flagge hat oben und unten einen roten Streifen.

The flag has a red stripe on the top and bottom.

Caption 48, Bundesländer und ihre Rezepte: Bundesland Berlin

 Play Caption

Ein gestreiftes Hemd und eine warme Hose und ganz schicke Schuhe.

A striped shirt and warm trousers and very stylish shoes.

Caption 17, Nicos Weg: Schick!

 Play Caption

In case you are like Nico and also like wearing patterned clothing, you might like to know that the word for "polka-dotted" is gepunktet, and kariert means "plaid," "checked," or "checkered." 

Further Learning
After you watch Eva's video on Yabla German in its entirety, look up the German words for some 3-D forms such as the pyramid, cone, cylinder, and prism. 

You are already familiar with adjectival possessive pronouns: instead of saying "the man's black hat" you may say "his black hat," etc. The main German singular possessive pronouns are ihr and sein, usually translated as "his" and "her."

BANNER PLACEHOLDER

In German, der Mann is a grammatically masculine noun, but in any language, a man is naturally masculine too: he is the male of the species. The same rule applies to die Frau: grammatically feminine in German, but naturally female. Thus, the possessive pronoun for der Mann is sein (his) and the possessive pronoun for die Frau is ihr (her), and it follows that the grammatical genders and natural genders are matching in these cases: 

Michael Jackson hielt im Übermut sein Baby aus einem Hotelfenster.

Michael Jackson held his baby boisterously out of a hotel window.

Captions 24-25, Berlin - Hotel Adlon feiert 15 Jahre Neueröffnung

 Play Caption

Astrid North hat ihr neues Album in Eigenregie produziert.

Astrid North has self-produced her new album.

Caption 28, Astrid North - Solo-Debüt

 Play Caption

The possessive pronoun of any grammatically masculine German noun is also masculine, just as any feminine noun takes a feminine pronoun. However, English does not translate the gender-specific sein and ihr respectively to "his" and "her" when referring to non-animate objects and many animals, but uses the gender-neutral "its" instead: 

… anhand eines massiven Sterns, der sein Leben aushauchte.

… based on a massive star which exhaled its last breath.

Captions 23-24, Unser Universum - Sternengeburt - Das Leben nach dem stellaren Tod

 Play Caption

Die Nordsee. Sieben Länder teilen sich ihre Küsten.

The North Sea: Seven countries share its coastlines.

Caption 10, Abenteuer Nordsee - Unter Riesenhaien und Tintenfischen

 Play Caption

As you see above, non-animate nouns follow their gender equivalents in German, but in English both are translated as "its" rather than "his" or "her." But how does German deal with pronouns of neuter nouns? 

Für jeden von uns bringt das neue Jahr seine ganz eigenen Herausforderungen mit sich.

For each one of us, the New Year brings its own very [unique] challenges with it.

Caption 2, Angela Merkel - Neujahrsansprache

 Play Caption

Im Wechsel der Gezeiten verändert das Watt ständig sein Gesicht.

With changing tides, the intertidal zone is continuously altering its appearance.

Caption 10, Abenteuer Nordsee - Unter Riesenhaien und Tintenfischen

 Play Caption

As you see in the examples above, German does not have a unique possessive pronoun for neuter nouns, but instead reverts to the masculine pronoun sein. This can lead to the rather odd situation of a grammatically neuter pronoun such as das Mädchen—which is naturally feminine in that "the girl" is a female of the species—taking the masculine pronoun sein: 

Schnell nahm das Mädchen ein neues Streichholz in seine zitternden Hände.

The girl quickly took a new match in her trembling hands.

Caption 37, Märchen - Sagenhaft - Das kleine Mädchen mit den Schwefelhölzern

 Play Caption

As you see, seine was translated to "her"—not "his"—in this case, because only "her" is correct in English. Although it is formally correct to use sein for das Mädchen, it is very common to see feminine pronouns such as ihr used for grammatically neuter but naturally feminine figures. In fact, in the video quoted above, every single pronoun reference to das Mädchen actually used grammatically incorrect feminine pronouns! So while it is good to be conscious of this rule, it won't sound unnatural if the occasional Mädchen winds up as ihr in your German!

BANNER PLACEHOLDER

Further Learning
Look on Yabla German for the possessive pronouns sein and ihr being used in a real-world context, and take a look at this previous Yabla lesson about possessive pronouns.