All of the words above are adverbs and can be translated as "again," and they are often interchangeable. However, they do have slightly different connotations, and this means that one adverb may be used in certain situations or expressions exclusively.

banner3 PLACEHOLDER

The adverb wieder is used to indicate repetition or a return to a previous state, though it may be uncertain exactly when this will occur. The connotation is "back again" or "repeatedly." You would not say nochmal da, nor would you switch out wieder in the two other expressions below. 

Wir sind wieder da auf Ganovenjagd

We are back again, chasing hoodlums

Caption 24, Die Pfefferkörner: Abschied tut weh

 Play Caption

Das sehen wir in dieser Stadt immer wieder.

We see this again and again in this city.

Caption 13, Architektur: der Stadt Karlsruhe

 Play Caption

Wir sind jetzt leider schon wieder am Ende der Sendung,

Unfortunately, we are now once again at the end of the program,

Caption 20, Abenteuer und Sport: Fallschirmspringen

 Play Caption

A casual shortening of noch einmal (literally "still one time"), the adverb nochmal suggests an immediate or additional repetition. The connotation is "another time," "a second time," or "one more time." As you might guess, danke nochmal is a standard expression, and neither wieder nor erneut would be used here. 

Danke nochmal, dass ihr mir geholfen habt, aber ich muss los.

Thanks again for helping me, but I have to go.

Caption 32, Die Pfefferkörner: Alles auf Anfang

 Play Caption

Ich wünschte, wir könnten uns heute nochmal begegnen.

I wish we could meet each other again today.

Caption 3, LOTTE: Zu jung

 Play Caption

Then there is erneut, which indicates "once again" and can have the connotation of a fresh attempt or starting over. You can remember this simply by the fact that the word neu is contained in the word, or by the related verb erneuern ("to renew," "to refresh"). Erneut is also slightly more formal than the other two adverbs, and can imply that something is inevitable or expected to repeat. 

Erneut rüsten sich die Murmeltiere für den Winter.

Once again, the marmots prepare for winter.

Caption 9, Wilde Schweiz: Sommer

 Play Caption

Die Prinzessin bat ihren Vater erneut um Rat.

The Princess asked her father for advice again.

Caption 65, Märchen - Sagenhaft Der Froschkönig

 Play Caption

Aber die Königin starb bald darauf und der König heiratete erneut.

But the Queen died soon afterwards and the king married again.

Caption 11, Märchen - Sagenhaft Schneewittchen

 Play Caption

Further Learning
You'll find many more examples to compare on Yabla German.

The three determiners above are generally used in more formal contexts. They come before a noun, and their endings change according to gender, case, and number, just like adjectives.

The determiner sämtlich is quite straightforward and is generally translated as "all," "all of them," or "all available." Here, you can see it used with plural nouns, which requires the addition of an -e, and one masculine singular noun, which requires -er. 

Er schöpft sämtliche Transportmöglichkeiten aus.

He exhausts all transportation options.

Caption 32, Wilde Schweiz: Sommer - Part 4

 Play Caption

Aber als es im Palast erschien, zog es sämtliche Blicke auf sich.

But when she appeared in the palace, she caught everyone's attention.

Caption 1, Märchenstunde: Das Aschenputtel

 Play Caption

Auch Fouls und sämtlicher Körperkontakt sind beim Ultimate nicht erlaubt.

Also fouls and all physical contact are not permitted in Ultimate [Frisbee].

Caption 14, Frisbee Karlsruher: Weihnachtsturnier

 Play Caption

The determiner jeglich means "any," "of any kind," or "every."  The -e ending is required for the two feminine nouns here:

Doch jegliche mangelnde Körpergröße macht der Buckelwal durch seine Wendigkeit und Lebhaftigkeit wieder wett.

But the humpback whale makes up for any lack of size with its agility and liveliness.

Captions 16-17, Evolution: Meeresbewohner

 Play Caption

Die Tanks sind allerdings schwer zu reinigen, sodass sie für jegliche Art von Bakterien eine pure Freude sind.

However, the tanks are difficult to clean, making them a pure joy for any kind of bacteria.

Captions 8-9, Galileo: Die fünf spannendsten Geheimnisse rund ums Fliegen

 Play Caption

Finally, etlich means "a number of," "several," or "quite a few." Again, we see an -e added for the plural nouns in the examples. 

Nach so schönen Bildern, ähm, hab' ich jetzt auch mal ein paar Profis gefunden, die schon etliche Male gesprungen sind.

After such beautiful images, er, I have now found a few professionals who have already jumped quite a few times.

Captions 19-20, Abenteuer und Sport: Fallschirmspringen

 Play Caption

In Deutschland leben etwa achttausend Halsbandsittiche, dazu kommen noch etliche Alexandersittiche.

About eight thousand Ring-necked Parakeets live in Germany, in addition, a number of Alexandrine Parakeets.

Captions 4-5, Freilebende Papageien Überwintern in Wiesbaden

 Play Caption

Further Learning
Try to create your own sentences with these determiners, or look for additional examples on Yabla German.